OTHER Self Study Program 841003 – Engine Management Systems SSP-841003-Engine-management-systems
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Engine
Management
Systems
Self Study Program
Course Number 841003
Page 2
Volkswagen of America, Inc.
Service Training
Printed in U.S.A.
Printed 4/2000
Course Number 841003
Part Number WSP 521 841 03
All rights reserved. All information contained
in this manual is based on the latest product
information available at the time of printing.
The right is reserved to make changes at any
time without notice. No part of this publication
may be reproduced, stored in a retrieval
system, or transmitted in any form or by any
means, electronic, mechanical, photocopying,
recording or otherwise, without the prior
permission of the publisher. This includes text,
figures and tables.
Always check Technical Bulletins and the
Volkswagen Worldwide Repair Information
System for information that may supersede
any information included in this booklet.
Page 3
Introduction ................................................................................................1
Course goals .................................................................................................2
Principles of engine operation ..................................................................3
Basic four-stroke principle ............................................................................3
Gasoline properties ......................................................................................6
Air/fuel mixture formation .............................................................................8
Fuel system, overview .................................................................................10
Evolution of Engine Management Systems .................................................11
Ignition system, overview ............................................................................12
Emissions system, overview ........................................................................18
Three-way Catalytic Converter, overview .....................................................20
On Board Diagnostics ..................................................................................22
Review ..........................................................................................................25
K-Jetronic/CIS .............................................................................................26
K-Jetronic with Lambda control ....................................................................28
KE-Jetronic/CIS-E ..........................................................................................29
KE-Motronic/CIS-E Motronic .........................................................................29
Digifant System Overview .........................................................................31
System description .......................................................................................31
Inputs/Outputs - Digifant II ...........................................................................33
Additional systems ......................................................................................33
On Board Diagnostics ...................................................................................35
Summary ......................................................................................................35
Review ..........................................................................................................37
Notes: ...........................................................................................................38
Motronic M2.9 Overview ...........................................................................39
System description .......................................................................................39
Inputs/Outputs - Motronic M2.9 ..................................................................43
On-Board Diagnostics ...................................................................................46
Signal usage ................................................................................................46
Motronic M2.9 Component Summary ......................................................47
Fuel system components ............................................................................47
Engine Control Module (ECM) J220 .............................................................48
Input sensors ................................................................................................49
Actuators (outputs) ......................................................................................63
Review ..........................................................................................................77
Mono-Motronic System Overview ...........................................................79
System Description ......................................................................................79
Inputs/Outputs ..............................................................................................81
Additional Systems ......................................................................................81
On Board Diagnostics ...................................................................................81
Summary ......................................................................................................81
Table of Contents
Page
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Table of Contents
Page
OBD-II Overview ........................................................................................83
Background ..................................................................................................83
OBD-II ...........................................................................................................84
OBD-II Function ............................................................................................85
Diagnostic Trouble Codes ...........................................................................86
Readiness Codes ..........................................................................................87
Summary ......................................................................................................88
Motronic M5.9 Overview ...........................................................................89
System Description ......................................................................................89
Input/Outputs - Motronic M5.9 ...................................................................90
Additional Systems .......................................................................................91
VR-6 system overview ................................................................................92
Inputs/Outputs - Motronic M5.9.2 ...............................................................94
1.8 liter turbo, system overview ..................................................................95
Motronic M5.9 Component Differences ...................................................97
Engine Control Module J220 ........................................................................97
Combined Sensors/Actuators .......................................................................98
Input sensors ................................................................................................102
Actuators (outputs) .......................................................................................104
Motronic M5.9.2 Component Differences ................................................107
Engine Control Module J220 ........................................................................107
Input Sensors ...............................................................................................108
Heated Oxygen Sensors ..............................................................................113
Actuators (outputs) .......................................................................................114
Review .........................................................................................................121
Motronic ME 7 ............................................................................................123
Pathways ......................................................................................................123
Components of Motronic ME 7 ....................................................................123
Electronic throttle control .............................................................................128
Review .........................................................................................................132
Level one course preparation ....................................................................133
Critical Thinking Skills ...................................................................................133
Volkswagen Electronic Service Information System (VESIS) navigation .......134
Volkswagen HELP line/Tech-tip line .............................................................134
Diagnostic and Special Tools ........................................................................135
Review questions .........................................................................................135
Suggested reading and reference ................................................................135
Glossary ......................................................................................................137
Volkswagen Engine Management Systems Teletest .............................141
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Introduction
Introduction
The origins of Volkswagen engine development can be traced back to a 1912 horizontally-opposed air-cooled overhead valve
aircraft engine designed and built by Dr. Ferdinand Porsche in Austria. This great-grandfather of the air-cooled Volkswagen engine
shared the same operating principles as the
most modern 5 valve per cylinder watercooled automotive engine.
Both engines are four-stroke reciprocating
internal combustion engines and, although a
direct comparison cannot be made, the basic
operating principles remain the same.
Technology moved the four-stroke engine
from magnetos and carburetors, to ignition
coils, points, distributors, mechanical fuel
injection, hydraulic fuel injection, electronic
ignition, electronic fuel injection, and finally to
the combined fuel and ignition control of the
most modern Motronic engine management
systems.
Motronic engine management systems use
electronics to precisely monitor and control
every aspect of engine operation, thereby
improving efficiency, power, and driveability,
while at the same time reducing fuel consumption and tailpipe emissions.
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Introduction
Motronic engine management systems control engine operation so precisely that it is no
longer possible to identify a separate emissions system. All functions previously identified as emissions system functions are now
components of Motronic engine management.
The intent of this program is to provide information that will yield a greater understanding
of engine management systems commonly in
use, and the progression leading to the newest Motronic ME 7 systems.
1980: K-Jetronic
with lambda control
Course goals
• Review principles of engine operation
• Explain the progression of engine
management systems used by Volkswagen
• Provide an in-depth understanding of both
previous engine management systems, and
the state-of-the-art engine management
systems in use today
1999: Motronic ME 7
1968: D-Jetronic
1965
1970
1976: K-Jetronic
1993: Motronic M2.9
1975 1980 1985 1990 1995 2000
1996: Motronic M5.9
1986: Digifant
SSP 8410/160
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Principles of engine operation
Principles of engine operation
Basic four-stroke principle
An internal combustion engine requires the
proper ratios of air and fuel, combined with a
properly timed spark for efficient combustion.
Operation of most automotive engines is
described in two upward and two downward
movements of the piston, called strokes.
These four strokes occur during two revolutions of the crankshaft and one revolution of
the camshaft. The complete process of cyclic
external spark ignition resulting in internal
combustion is called the “Otto cycle.”
All four-stroke engines operate in the same
manner, regardless of the number of cylinders, although an engine with multiple cylinders has more firing pulses, resulting in a
smoother running engine.
Intake stroke (1)
The first phase of engine operation begins
with the intake valve opening and the piston
moving down into the cylinder. This draws air
and atomized fuel into the cylinder.
Compression stroke (2)
Operation continues with the piston at the
bottom of its stroke, and the intake valve closing. The piston moves up in the cylinder, compressing the air/fuel mixture. Near the end of
the stroke the air/fuel mixture is ignited by the
ignition system.
Combustion (power) stroke (3)
As the air/fuel mixture burns it expands, creating pressure within the cylinder, pushing the
piston down. This provides the motion which
turns the crankshaft.
Exhaust stroke (4)
The exhaust valve opens near the end of the
power stroke and the piston moves up. The
burned gases are pushed up and out the
exhaust port, and the cycle is repeated.
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Principles of engine operation
Mechanical systems
Several support systems are required to make
the combustion process occur continuously.
The valvetrain operates the valves, the lubrication system supplies the oil, the cooling system removes heat, and the electrical system
supplies the voltage. The engine management system delivers fuel and spark to match
the air demands of the engine.
Because of heat and drag, the thermal efficiency of a typical gasoline engine is around
25% (approximately one fourth of the heat
energy of the fuel is converted into usable
engine power).
Mechanical integrity
The mechanical condition of the cylinder
directly influences the combustion process.
Conditions within the combustion chamber
can also be influenced by other factors,
including:
• Camshaft timing
The following diagnostic tests are used to
check cylinder condition:
• Compression test:
This test can be useful in evaluating condition of the piston rings, head gasket
and valve sealing ability when used in
conjunction with other diagnostic tests.
A compression test requires the removal
of all the spark plugs. A pressure gauge
is then threaded into the spark plug hole.
The engine is cranked while applying
Wide Open Throttle (WOT) until the pressure stops increasing. Pressure gauge
readings are then compared to factory
specifications.
To ensure the accuracy of the test, the
engine should be at normal operating
temperature.
• Oil pressure
• Restrictions in the intake or exhaust paths
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Principles of engine operation
• Cylinder leakdown test
A cylinder leakdown test is especially
useful to identify sources of cylinder leakage. As an example, a hissing sound
heard at the tailpipe while the test is
being performed indicates possible leaking exhaust valves.
A cylinder leakdown test also requires
the removal of the spark plugs, but
necessitates that the crankshaft be
turned so that the piston is at the top of
the compression stroke (Top Dead Center or TDC) with both valves closed. A
measured amount of compressed air is
applied the cylinder through the spark
plug hole using a leakdown tester. The
pressure of the air in the cylinder is compared to the pressure being applied. A
“percentage of leakage reading” is given
by the gauge. The reading is compared to
adjacent cylinders to determine cylinder
condition.
Summary
For any combustion process to occur, proper
air/fuel mixture and a source of ignition are
required. For an internal combustion engine to
operate, the air/fuel mixture must be compressed, and the spark must occur at the
proper time to create the combustion that is
the motive force used to drive the piston.
The mechanical systems must all work
together to draw the combustible mixture into
the cylinder, to compress it, to extract maximum power from combustion and to expel
what remains after the combustion process.
These systems work together to provide the
support necessary to keep the engine running.
As in the compression test, the engine
should be at normal operating temperature to ensure the accuracy of the test.
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Principles of engine operation
Gasoline properties
For the engine management system to allow
the engine to operate at peak efficiency and
power, the octane rating of the gasoline must
be within factory specifications as outlined in
the owner’s manual.
Octane is a relative measure showing the
gasoline’s ability to resist self-ignition due to
heat and pressure within the cylinder. Self
ignition of the fuel is known as knocking (detonation) or pinging (pre-ignition).
• Pinging:
When the air/fuel mixture ignites before
the spark occurs.
• Knock:
When a pressure wave from spark igniting the fuel creates a secondary combustion, causing the two pressure waves to
collide.
Gasoline with higher octane numbers resist
temperature and pressure better, and therefore have less tendency to self-ignite.
The CLC number is derived from both the
RON and the MON as follows:
RON + MON
= CLC
2
SSP 8410/158
The CLC number was later changed to the
Anti-Knock Index (AKI) number. Gasolines
identified as “regular” generally have an AKI
number of around 87, while gasolines identified as “premium” generally have an AKI
number around 92.
AKI numbers apply to gasoline that is freshly
pumped. Gasoline that is exposed to the air
for extended periods of time undergoes a
decrease in AKI number due to evaporation
and oxidation.
Gasoline Octane vs. Burn Speed
94
93
Several methods of measuring octane are
used worldwide. These include the following:
• Research Octane Number (RON); tests
resistance to knock at lower engine speeds.
• Motor Octane Number (MON); tests
resistance to knock at higher engine
speeds.
In an effort to simplify a confusing array of
octane numbers, the United States Government enacted legislation requiring the posting
of a number on the dispensing pump reflecting the minimum octane number as determined by the Cost of Living Council (CLC).
6
92
91
90
89
88
AKI Number
87
86
85
84
Fast
Burn Time
Slow
SSP 8410/25
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Principles of engine operation
Modern pump gasoline contains a wide variety of additives to help obtain optimal engine
and fuel system operation. The additive package added to the base gasoline will include at
least the following:
• Anti-aging additives
• Intake contamination inhibitors (detergents)
• Corrosion inhibitors
• Icing protection
• Anti-knock additives
Different concentrations of additives, along
with other blending considerations, are used
according to market and seasonal demands.
All Volkswagen Owner’s Manuals list recom-
mended fuel grade specifications, along with
notes on the use of fuels containing methanol, ethanol and MTBE (methyl tertiary butyl
ether).
• Octane must be between 87 AKI and 93
AKI, but exact requirements depend on
model and year.
• MTBE is blended with gasoline and sold in
some areas of the country as oxygenated
fuel to help reduce tailpipe emissions. This
fuel can be used as long as specific
percentage requirements are maintained
and octane minimums are met.
• Methanol and ethanol are types of alcohol
commonly mixed with gasoline. Fuel with
these additives can be used as long as
specific percentage requirements are
maintained and octane minimums are met.
These requirements vary from year to year.
The combustion process is dependent on the
correct grade and quality of gasoline. If gasoline sits for an extended period of time, the
octane can evaporate from the fuel, creating a
varnished residue. This can restrict injector
flow and fuel pump/fuel line performance.
This can lead to hard starting, reduced performance and no code driveability complaints.
Note:
MTBE has been identified by the Government
as a possible carcinogen and is being phased
out in automotive use.
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Principles of engine operation
Air/fuel mixture formation
The function of the fuel system is to deliver
the correct air/fuel mixture to the engine.
The optimal air/fuel ratio for complete combustion is 14.7 parts air to 1 part fuel by mass.
This is referred to as the stoichiometric
ratio.
Mixture corrections must be made as
required to satisfy the differing engine
demands encountered under any given driving condition.
Engine operating conditions include:
• Idle:
For a smooth and efficient idle, the air/fuel
mixture must be 14.7:1 (stoichiometric
ratio).
Definition:
A rich mixture contains more fuel than air in
relation to the stoichiometric ratio.
A lean mixture contains more air than fuel in
relation to the stoichiometric ratio.
• Part throttle:
Most automotive engines spend the largest
part of their operational life running at part
throttle and fuel delivery is calibrated to
yield minimum consumption (maximum
economy).
• Full throttle:
Mixtures containing a higher proportion of
fuel (richer) provide more power at the
expense of economy.
• Transition:
Both gradual and sudden changes in engine
speed and load require instantaneous
mixture correction. Transition from open to
closed throttle plate tends to give a higher
proportion of fuel, whereas transition from
closed to open tends to give a higher
proportion of air.
• Cold start:
During cold start and warm-up phases of
engine operation, the fuel condenses on
the cold cylinders, creating a lean condition,
resulting in incomplete combustion. To
counteract this, the fuel mixture is enriched.
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Principles of engine operation
The fuel system must be able to quickly
respond to and satisfy these widely varying
operating conditions.
The air/fuel mixture is referred to by the Greek
letter λ (Lambda), and is generally referencing
the air factor in the ratio. Listed below are
several common λ operating ranges:
• λ = 1: mixture is optimum (stoichiometric).
• λ < 1: mixture is rich (lacking air) typically in
the range λ = 0.85 to 0.95.
• λ > 1: mixture has an excess of air; a lean
mixture typically in the range λ = 1.05 to
1. 3 0 .
• λ > 1.30: mixture has too much air to
support consistent combustion.
On an engine at normal operating temperature, it is important to maintain λ = 1. This
allows for optimal catalytic converter operation (although in actual practice, λ factors
between 0.9 and 1.1 provide the best engine
operation).
Because of the importance of the fuel mixture
under a variety of operating conditions, the
air/fuel mixture must be adapted constantly.
In modern fuel systems, a feedback loop
using oxygen sensors for the primary input is
used for this adaptation.
The period of time after an engine start when
the oxygen sensor is not at operating temperature, and therefore not used, is called open
loop operation. This condition can occur
after either a cold or warm start. Conversely,
engine operation with a valid oxygen sensor
signal is called closed loop operation.
For more information on open loop operation
and closed loop operation, please refer to the
glossary.
Note:
For more information regarding oxygen sensor function, refer to the Motronic M2.9 component overview.
Control module
enriches mixture
Closed Loop Operation
O2 sensor
shows rich mixture
2 sensor
O
shows lean mixture
Control module
leans mixture
SSP 8410/190
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Principles of engine operation
Fuel system, overview
The fuel system is made up of numerous individual components. The purpose of these
components is to insure delivery of the correct air/fuel mixture formation to the engine at
the correct time.
Components such as fuel pumps and carburetors represented the state-of-the-art technology in early systems, but mechanical
limitations prevented further development.
Although advantages of these systems
include simplicity and relatively low cost, disadvantages are frequent maintenance, poor
emissions, relative inefficiency, and the inability to be self-diagnosing.
Due to limited interaction between individual
components, control of fuel delivery was not
precise enough to meet modern standards.
The advent of solid-state electronics allowed
improvements in many fuel system areas.
Sensors were able to provide information on
current engine operating conditions. A central
control unit would then process the data,
make the calculations, and signal the appropriate actuators that would, in turn, run the
engine. This level of control far exceeded the
abilities of a carburetor and its related
mechanical systems, and led to widespread
use of fuel injection.
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Evolution of Engine Management Systems
Principles of engine operation
Modern electronics created a new perspective in how fuel and ignition system management is viewed. Starting with the Type III in
1968, Volkswagen began integrating electronics into the fuel system. The Bosch™ DJetronic™ fuel injection system that was
used seems very basic by today’s standards,
but it represented a giant technological leap at
the time. The analog electronic control unit
managed fuel delivery to two pairs of fuel
injectors. The ignition continued to be handled
by a breaker point distributor.
Advances in computer technology, combined
with new circuit designs, allowed control of
more than just fuel. Shared sensor technology
allowed the signal from a temperature sensor,
for example, to be used for several different
functions.
Mixture control feedback through the use of
oxygen sensors allowed more precise metering of the fuel. Ignition system feedback
through the use of knock sensors allowed
optimum spark timing (feedback loops).
Digital data processing and micro-processor
technology made it possible to take extensive
operating information from sensors and other
input sources, and convert it to program-mapcontrolled fuel injection and ignition data.
Today, technology enables engine management systems to control not only emissions
and driveability, but to constantly optimize
engine torque as well.
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Principles of engine operation
Ignition system, overview
The ignition system’s function is to insure
delivery of a correctly timed and sufficiently
strong spark to ignite the air/fuel mixture.
Electrically, the ignition system components
are divided into two categories by voltage
level. Components using battery or low voltage are classified as primary, and include the
following:
• Battery
• Ignition coil (primary windings)
• Trigger (either breaker points or electronic)
• Electronic signal amplification and advance
control
Components using high voltage are classified
as secondary, and include the following:
• Spark plugs and wires
• Distributor cap, rotor
• Ignition coil (spark plug side)
System function
Refer to the basic coil ignition with breaker
points graphic at the bottom of this page.
When the ignition is switched on, battery voltage is supplied to the low voltage or primary
side of the ignition coil. A strong magnetic
field is developed in the primary windings.
When the Ground side of the coil is open (by
breaker points or Hall sender), the magnetic
field around the primary windings collapses
and induces a higher voltage in the secondary
windings.
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Simply stated, the ignition coil is a step-up
transformer switched on and off by the trigger
unit.
The high voltage generated by the ignition coil
is distributed to each spark plug in the proper
order through the distributor cap as the distributor shaft turns. At the spark plug, the high
voltage causes an electrical spark to arc from
the center electrode to the Ground electrode
and spark plug threads.
The period of time that the negative side of
the coil is grounded (points remain closed) is
referred to as dwell. Dwell is the length of
time the primary winding can generate a magnetic field. The longer the dwell time, the
stronger the magnetic field. This results in a
higher secondary voltage (stronger spark).
Principles of engine operation
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Principles of engine operation
In a breaker point style ignition system, the
ignition points are mounted to a movable
mechanism in the distributor called the
breaker plate. They are switched on and off by
the action of a rubbing block working against
lobes of a cam on the distributor shaft. The
distributor shaft turns at the same speed as
the camshaft (1/2 crankshaft speed). A condenser (also called a capacitor), is connected
in parallel with the ignition points, and acts as
a filter to prevent point arcing.
The inherent drawback to the breaker points
system is mechanical wear (requiring periodic
maintenance). To eliminate this, the solid
state ignition system was developed. By
replacing the ignition points with a Hall
sender, more consistent and reliable ignition
system performance was attained.
The Hall sender is a solid-state, semi-conduc-
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Principles of engine operation
tor device mounted in the distributor housing.
A rotating trigger wheel is passed between a
magnet and a Hall-effect transistor (see Glossary). Windows in the trigger wheel allow the
Hall-effect transistor to be exposed to the
magnetic field causing current to flow through
the transistor. When a shutter wheel vane
blocks the magnetic field to the Hall-effect
transistor, current flow stops.
Operating voltage is supplied by either an igni-
Advantages of Hall Sensor vs. Breaker Point Ignition
Available voltage
Primary current capacity
Secondary coil energy
Spark duration at plug
Hall-effect
ignition
25,000 volts
7.5 amps
80 mWs
3.4 ms
Breaker point
ignition
18,000 volts
3.5 amps
30 mWs
3.2 ms
tion control module or the engine control
module. Through these control modules, the
Hall sender switches off the ignition coil when
current flows (exposed) and on when there is
no current flow (blocked).
Advantages include:
• High speed switching
• No mechanical wear
• No maintenance
The accompanying table highlights the performance advantages.
Newer engine management systems take the
Hall signal a step further, and combine it with
computer control to provide even more precise spark control.
SSP 8410/157
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Principles of engine operation
Ignition advance
It takes approximately 2 milliseconds (0.002
seconds) from the start of mixture ignition to
complete combustion. This time remains consistent for all engine speeds, but the time
available for the process to occur is reduced
as engine speed increases (the piston is moving faster). For this reason, spark must be
generated sooner.
The process of starting the ignition spark
sooner in the cycle is called ignition advance.
Ignition advance must be adjusted to account
for wide variations in engine operating conditions, with primary concern given to engine
speed and engine load.
At idle, the start of combustion can occur
near the top of the compression stroke. This
allows maximum combustion pressure to
push the piston down during the power
stroke.
Note:
Spark ignition engines produce the greatest
power, and are the most efficient, when ignition occurs just before the point of detonation.
As engine speed increases, the spark must
be generated sooner, so that maximum cylinder pressure will continue to occur as the piston starts down on the power stroke.
In the basic ignition system described previously, the cam which operates the breaker
points is connected to a mechanism where
centrifugal fly-weights move the cams position in relation to points position in the distributor.
This allows the spark timing to change with
engine speed. The faster the engine speed,
the sooner the spark occurs.
The breaker plate is also attached to a vacuum
diaphragm. This allows the spark timing to
change in relation to an engine vacuum signal
that changes with engine load.
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Spark plugs
Principles of engine operation
Spark plugs represent the end component in
the ignition system. They must endure the
high temperatures and pressures of the combustion chamber for millions of ignition operating cycles without failure.
An important characteristic of any spark plug
is its ability to dissipate heat. Classifications
exist for hot or cold or anywhere in between.
A cold spark plug is a one that transfers the
heat from the combustion process rapidly
through the threads to the head and cooling
system.
A hot spark plug is a one that transfers the
heat from the combustion process slowly
through the threads to the head and cooling
system.
Different engine types require spark plugs
with different physical characteristics, as well
as electrical characteristics, and are supplied
by several different manufacturers. Since
spark plug characteristics are specified for
each particular engine type by the factory, it is
advisable to stay within these recommendations.
For the heat transfer process to the cylinder
head to be effective, the spark plug must be
properly torqued into a cold cylinder head
(refer to VESIS).
Note:
To ensure the integrity of the ground through
the threads, anti-seize or similar products
should never be applied to the spark plug
before installation.
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Principles of engine operation
Emissions system, overview
Air quality has been an environmental concern for many years. Pollution from numerous
sources, combined with atmospheric conditions, resulted in the degradation of air quality
in many of the industrialized areas of the
world. The State of California recognized that
automobile emissions contributed significantly to the rising levels of pollution, and
enacted legislation to establish air quality
standards for motor vehicles. Other states
continue to adopt California emissions standards.
The first emissions requirement was to control crankcase emissions through Positive
Crankcase Ventilation (PCV). The 1963 Type I
Beetle engine pictured on page 1 shows compliance with this requirement. This is the first
Volkswagen emission controlled engine.
Federal and state clean air legislation continued to be passed with California leading the
rest of the nation. In an effort to reduce
exhaust emissions, various parts of the fuel
and ignition systems were modified.
New systems were added and existing systems were modified to reduce tailpipe and
crankcase emissions. Systems were also
added to reduce emissions from the fuel tank
and vent system.
A basic emissions system may have the following components:
• Throttle positioners and dashpots
• Exhaust gas recirculation
• Oxidation catalytic converters
• Oxygen sensors
• Secondary air injection
• Intake air pre-heating
• Evaporative emissions (fuel tank)
• Crankcase emissions
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Principles of engine operation
It was soon clear that a more advanced
means of managing fuel, air and ignition was
needed to meet the changing Federal and
State emissions requirements and fuel economy standards. Excellent driveability, performance and economy had to be maintained,
and at the same time ensuring low exhaust
emissions.
Testing indicated that fuel vapor escaping into
the atmosphere contained more hydrocarbons than the exhaust emissions of the vehicle. As a result, the Evaporative Emissions
(EVAP) return system was added to minimize
the amount of fuel vapor released.
Vapors are stored in a charcoal canister, and
then passed along via the EVAP canister
purge regulator valve to the engine to be consumed in the combustion process.
Current Motronic engine management systems also use a Leak Detection Pump (LDP)
to pressurize the evaporative return system to
insure the integrity of the system (checks for
leaks). Fuel vapors that escape to the atmosphere are reduced to a minimum. Systems
after 1998 include On Board Refueling Vapor
Recovery (ORVR) systems to control fuel
vapor emissions during refueling.
All of these efforts are contributing to the
reduction of harmful pollutants that escape
into the atmosphere. For more information
see SSP 841903, EVAP Systems, Operation
and Diagnosis.
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Principles of engine operation
Three-way Catalytic Converter, overview
The catalytic converter is a major component
in exhaust emission control “downstream” of
the combustion process. Development and
common usage of this device began with
open-loop versions of carburetor and fuel
injection systems in the 1970s. Closed loop
engine management systems required by current legislation in the United States and Canada insure that almost all internal combustion
engined vehicles are equipped with this
important component.
A catalyst, by chemical definition, is any substance that promotes, accelerates, or initiates
a chemical reaction without being consumed
in the reaction itself. In the case of the automotive catalytic converter, the active catalyzing agents are platinum, rhodium, and/or
palladium.
N
NO
x
CO
2 +
HC
2
CO
H2O
CO
2
Catalyst coat
For maximum efficiency, the internal surface
area exposed to the exhaust flow must be as
large as possible. For that reason, the catalyzing agents are deposited by evaporation
onto a ceramic or metallic sub-structure called
a monolith. The monolith is a long-channel
honey-comb shaped structure with a large
surface area contained in a high temperature
steel housing. The surface area is increased
even more through a process where a “wash-
coat” is applied. Other types of converters
are used by other automotive manufacturers,
but all Volkswagens use the ceramic or metallic monolith design.
Catalytic converters operate most efficiently
at high temperatures and are usually placed in
the exhaust stream as close to the engine as
possible.
A modern three-way catalytic converter is so
named because it takes the three major automotive pollutants and reduces and oxidizes
them into relatively harmless substances that
do not contribute to air pollution.
20
O2 sensor
Wash-coat
Base material
(substrate)
SSP 8410/189
O2 sensor
SSP 8410/121
Page 25
Catalytic Converter Operation
Principles of engine operation
The three-way catalytic converter takes the
major exhaust pollutants of:
• NO
• HC (hydrocarbons)
• CO (carbon monoxide)
and breaks them down into their component
chemicals through a two-part process.
The first part of the operating process is the
catalytic reduction of the NO
This phase reduces the nitrous oxides to their
basic elements of nitrogen and oxygen. Since
the air we breath is roughly 78% nitrogen,
this is an acceptable result. The liberated oxygen is roughly 21% of the air and it too, is
acceptable. However, the oxygen remains in
the converter where it is used for the oxidation part of the process.
The second part of the operating process is
the catalytic oxidation of the HC and CO components. This phase combines the oxygen
from the previous phase with the oxygen
already contained in the monolith to produce
water and carbon dioxide. Both of these compounds are essentially harmless.
(nitrous oxides- several)
x
component.
x
The output from a normally operating threeway catalytic converter consists primarily of:
• N
(nitrogen)
2
• CO2 (carbon dioxide)
• H2O (water)
The reduction process is most efficient in a
low O
cess is most efficient in a high O
ment.
It is the job of the engine management system to regulate the exhaust gas mixture to
obtain the optimum environment for the
reduction and oxidation process to occur. For
maximum efficiency within the converter,
lambda (λ) must be at 0.99 or 1.00 for both
reactions. This operating range is referred to
as the lambda (λ) window.
The data required for this closed-loop control
process is provided by the oxygen sensors
(illustration SSP 8410/121 on previous page).
Oxygen sensor functionality varies by engine
management system. Please refer to the
appropriate chapter for system specific oxygen sensor information.
environment, and the oxidation pro-
2
environ-
2
21
Page 26
Principles of engine operation
On Board Diagnostics
On Board Diagnostic (OBD) capability allows
the Engine Control Module (ECM) to recognize faults that could indicate a problem with
a component or associated wiring. When a
fault is recognized, a Diagnostic Trouble Code
(DTC) will be stored in DTC memory.
Current federal regulations require that any
fault that affects exhaust emissions, or the
monitoring of exhaust emissions, sets a Diagnostic Trouble Code (DTC), and illuminates a
Malfunction Indicator Light (MIL) to alert the
operator of an emissions related failure.
Engine Control Module (ECM) fault
recognition
Volkswagen engine management systems
have the ability to diagnose and identify several different component failure conditions,
including:
• Short circuit to Battery Positive (B+)
• Open circuit/Short circuit to Ground
Systems complying with OBD II regulations
also identify implausible signals. An implausible signal is a reading that is considered out of
range for operating conditions. This is covered
in the OBD II section of this SSP.
ECM inputs (sensors) and outputs (actuators)
are powered in one of two ways:
• The ECM supplies a ground signal and the
B+ is supplied from the fuse/relay panel.
• The ECM provides a reference voltage and
monitors the voltage drop across the
sensor’s resistance (e.g. engine coolant
temperature sensor).
22
Page 27
Principles of engine operation
Component Ground controlled via ECM
The following examples illustrate a solenoid
valve in a circuit that receives a constant 12
Volt source from the fuse/relay panel with
component Ground controlled via the ECM.
Normal operation of the component is
checked by the self diagnosis circuitry in the
ECM. The ECM monitors the voltage drop.
This will change from 12V when the solenoid
is in-active (open circuit voltage) to approximately 0V when the solenoid is active (voltage drops across the consumer). If the selfdiagnosis circuitry does not see the correct
voltage drops during operation of the component, the appropriate DTC is stored.
Short circuit to B+
If a short circuit exists in the wiring harness,
harness connector, or in the component itself,
the input to the ECM is a constant positive
voltage. The ECM recognizes this as an
abnormal condition, and a DTC is stored.
Open circuit/Short circuit to Ground
If an open or short circuit exists in the wiring
harness, harness connector, or in the component itself, the input to the ECM is a constant
Ground (0 Volts). The ECM recognizes this as
an abnormal condition, and a DTC is stored.
To determine the exact failure, additional testing is required.
Scan tool display:
• Open circuit/ Short circuit to Ground
Scan tool display:
• Short circuit to positive (B+)
23
Page 28
Principles of engine operation
Component power (B+) controlled via ECM
The following examples illustrate a temperature sensor in a circuit that receives a constant 5 Volt reference source from the ECM.
It also can receive a Ground from a variety of
sources for signal accuracy. In this type of circuit, as the temperature changes the resistance changes, resulting in a varying voltage
drop across the sensor.
During normal operation the self diagnosis circuitry monitors the 5V reference and the voltage drop across the component. The ECM
“watches” for a valid signal, which varies by
component, but will not equal either 0 or 5
Volts. If Battery +, Ground or the 5V reference
is seen by the ECM, an appropriate DTC is
set.
Short circuit to Ground
Open circuit/Short circuit to B+
If an open or short circuit exists in the wiring
harness, harness connector, or in the component itself, the input to the ECM is a constant
5 Volts. The ECM recognizes this as an abnormal condition, and a DTC is stored.
Scan tool display:
• Open circuit/ Short circuit to B+
A break in the wiring harness insulation short
circuits the 5 Volt output to Ground. The input
to the ECM is a constant Ground (0 Volts).
The ECM recognizes this as an abnormal condition, and a DTC is stored.
Scan tool display:
• Short circuit to Ground
24
Page 29
Review
Principles of engine operation - Review
1. Technician A says that Motronic
engine management systems can
identify short circuits to positive with
some system components.
Technician B says that Motronic
engine management systems can
identify short circuits to Ground with
some system components.
Which Technician is correct?
a. Technician A only
b. Technician B only
c. Both Technician A and Technician B
d. Neither Technician A nor Technician
B
2. Which of the following is NOT an oper-
ating requirement for efficient operation of the Three Way Catalyst?
a. High operating temperature.
b. Lambda (λ) window of 0.99 to 1.00.
c. Gasoline without lead or lead com-
3. In the four-stroke gasoline engine, the
pounds.
d. Gasoline with a minimum octane of
87 AKI.
camshaft turns at what speed in relation to the crankshaft?
4. Which of the following components is
NOT a component of gasoline’s ability
to pre-ignite?
a. Research octane number
b. Motor octane number
c. Cetane
d. Anti-knock index
5. Which of the following is NOT a component failure condition recognizable
by the scan tool?
a. Short circuit to positive
b. Short circuit to neutral
c. Short circuit to Ground
d. Open circuit
6. Technician A says that the ignition coil
is part of both the primary and the
secondary sides of the ignition system.
Technician B says that the distributor
rotor is part of the primary side of the
ignition system.
Which Technician is correct?
a. Technician A only
b. Technician B only
c. Both Technician A and Technician B
a. Twice crankshaft
b. Same as crankshaft
c. ¼ crankshaft
d. ½ crankshaft
d. Neither Technician A nor Technician
B
7. Which of the listed exhaust by-products is NOT harmful to the atmosphere?
a. Hydrocarbons (HC)
b. Oxygen (O
c. Carbon monoxide (CO)
d. Oxides of Nitrogen (NO
)
2
)
x
25
Page 30
Notes
26
Page 31
K-Jetronic/CIS
K-Jetronic
In 1976, Volkswagen introduced Bosch KJetronic, or CIS, fuel injection on the Dasher
model. This early hydro-mechanical fuel system provided efficient and consistent running
characteristics.
Continuous Injection System (CIS) operates
by controlling fuel flow rates and variable
pressures to the fuel injector. As the name
implies, the fuel injectors are constantly
injecting fuel. When the intake valve is
closed, the fuel is stored in the intake port.
Opening the valve allows the stored fuel to be
pulled into the cylinder.
Fuel for the injectors is provided by the fuel
distributor. This component is directly linked
to the air flow sensor. Any increase in airflow
provides a proportional increase in fuel flow to
the injectors.
Fuel pressure is controlled by a control pressure regulator, or warm-up regulator.
The control pressure regulator supplies pressure to the top of the control plunger, and
depending on how much pressure is applied,
will create a resistance for the plunger to rise,
affecting the fuel mixture.
Example:
On a cold start, control pressure is 0.5 bar. As
a result, there is little resistance for the
plunger to rise with movement of the air flow
sensor. As operating temperature rises, control pressure increases to 3.7 bar, hence there
is greater resistance, resulting in a leaner fuel
mixture.
27
Page 32
K-Jetronic
Baseline air/fuel mixture is accomplished by
adjusting the rest position of the control
plunger. The design of the system is such that
the fuel mixture will scale according to this
baseline setting.
Cold start enrichment is handled by a separate electrically operated fuel injector
mounted in the intake manifold. Power is provided via Terminal 50 from the ignition switch.
The Ground is completed through a Thermotime switch mounted in the cylinder head.
The Thermo-time switch has a bi-metallic strip
that is heated by 12 Volts also supplied by Terminal 50. Heating the strip causes it to flex
and open the circuit. This “timer” circuit
allows for a temperature sensitive quantity of
fuel to be injected during cranking of the
engine. If coolant temperature is above
roughly 35° C, the heat of the engine will not
allow the cold start injector to operate.
Additional airflow during cold running is handled by an auxiliary air bypass valve. A heated
bi-metallic strip opens a passage in the valve.
This allows a controlled excess of air during
the warm-up period of the engine. As the
engine enters warm running, the passage is
closed and idle air quantity defaults to a
bypass channel in the throttle valve housing.
28
Page 33
K-Jetronic with Lambda control
K-Jetronic
In 1980, CIS fuel injection was modified to
better meet exhaust emission standards.
The addition of an oxygen sensor allowed the
fuel system to adapt to running conditions.
This provided more consistent running characteristics, as well as minimizing the amount of
adjustment neccesary to the system.
The control unit is able to adjust fuel trim by
continually modifying the differential pressure between the upper and lower chambers
of the fuel distributor. A solenoid valve (frequency valve) is installed inline between the
system pressure from the lower chamber and
the control presssure in the lower chamber.
After the engine has reached operating temperature it enters closed loop operation (see
Glossary). The control unit pulses the frequency valve with a varying duty cycle, thus
varying the differential pressure.
The baseline air/fuel mixture is no longer set
be means of sampling pre-catalyst exhaust
gases. A test connector is provided to test the
duty cycle of the valve. During closed loop
operation the duty cycle should fluctuate
between 45%-55%. The fluctuations follow
the voltage output of the oxygen sensor.
The Lambda control unit receives input from
the oxygen sensor, as well as an idle and full
throttle switch.
This system was the beginning of today’s
adaptive engine management systems.
29
Page 34
K-Jetronic
KE-Jetronic/CIS-E
For the 1985 model year, Volkswagen
expanded the capabilities of the CIS fuel injection system. New features include:
• Warm-up regulator replaced with
electrically operated solenoid valve
• Electrically heated oxygen sensor (allows
for faster closed loop operation)
• Air flow sensor potentiometer (more
accurate control of Lambda)
• Altitude sensor (varies fuel trim with
barometric pressure)
• Idle stabilizer valve (more stable idle
characteristics)
The major change for the CIS-E system is the
replacement of the control pressure regulator
with a Differential Pressure Regulator (DPR).
This electro-mechanical valve receives a varying amperage from the CIS-E control unit; as
amperage is increased control pressure is
decreased. This increases fuel flow to the
injectors.
KE-Motronic/CIS-E Motronic
For the 1990 model year, the 16-valve 2.0 liter
engine received the last change to the KJetronic system.
CIS-E Motronic intergrated fuel and ignition
timing in one common control unit, as well as
the following features:
• Oxygen sensor control with adaptive
learning
• Dual map ignition control with cylinder
selective knock control
• EVAP purge control
• Permanent fault memory with self
diagnosis
For more information regarding knock control,
and adaptive learning (refer to Glossary).
This change allowed for more accurate control
of the fuel trim, as well as decreased mainte-
nance.
30
Page 35
Digifant System Overview
System description
Digifant
Digifant Engine Management was first introduced on the 1986 2.1 liter Volkswagen
Vanagon engine. This system combined digital fuel control as used in the earlier Digi-Jet
systems with a new digital ignition system.
Digifant as used in Golf and Jetta models simplified several functions and added knock sensor control to the ignition system. Other
versions of Digifant appeared on the Fox, Corrado, and Eurovan in both the United States
and Canada.
Fuel injection control is digital electronic. It is
based on the measurement engine load (Air
Flow sensor), and on engine speed (Hall
sender). These primary signals are compared
to a map, or table of values, stored in the
Engine Control Module (ECM) memory.
The amount of fuel is controlled by the injector opening time (duration). This value is taken
from a program in the ECM that has 16 points
for load and 16 points for speed. These 256
primary values are then modified by coolant
temperature, intake air temperature, oxygen
content of the exhaust, battery voltage and
throttle position to provide 65,000 possible
injector duration points.
31
Page 36
Digifant
The fuel injectors are wired in parallel, and are
supplied with constant system voltage. The
ECM switches the Ground on and off to control duration. All injectors operate at the same
time each crankshaft revolution; two complete revolutions being needed for each cylinder to receive the correct amount of fuel for
each combustion cycle.
Ignition control is also digital electronic. The
sensors that supply the engine load and
engine speed signals for injector duration provide information about the basic ignition timing point. The signal sent to the Hall control
unit is derived from a program in the ECM
that is similar to the injector duration program.
There are 16 points available for load and 16
points for speed. The resulting 256 single
operational points are modified by coolant
temperature signals and cylinder selective
knock control (where applicable) to achieve
the optimal ignition point.
Knock control is used to allow the ignition timing to continually approach the point of detonation. This point is where the engine will
produce the most power, as well as the highest efficiency. For more information on knock
control function refer to the appropriate section in Motronic M2.9.
Additional functions of the ECM include operation of the fuel pump by closing the Ground
for the fuel pump relay, and control of idle
speed by a throttle plate bypass valve. The
idle air control valve (previously known as an
idle air stabilizer valve), receives a changing
milliamp signal that varies the strength of an
electro-magnet pulling open the bypass valve.
Idle speed stabilization is enhanced by a process known as Idle Speed Control (ISC). This
function (previously known as Digital Idle Stabilization), allows the ECM to modify ignition
timing at idle to further improve idle quality.
32
Page 37
Digifant
Inputs/Outputs - Digifant II
The 25-pin electronic control unit used in the
Golf and Jetta receives inputs from the following sources:
• Hall sending unit (engine speed)
• Air flow sensor (engine load)
• Coolant temperature sensor
• Intake air temperature sensor
• Oxygen sensor
• Throttle position switches
• Knock sensor
Additional signals used as inputs are:
• Air conditioner (compressor on)
• Battery voltage
• Starter signal
The anti-lock brake system, 3-speed automatic transmission and vehicle speed sensor
are not linked to this system.
Additional systems
The evaporative emission system is controlled
by a vacuum operated mechanical carbon canister control valve.
Fuel pressure is maintained by a vacuum
operated mechanical fuel pressure regulator
on the fuel injector rail assembly.
Inputs and outputs are shown in the following
illustration. Digifant II as used on Golf and
Jetta vehicles provides the basis for this chart.
Outputs controlling engine operation include
signals to the following:
• Fuel injectors
• Idle air control valve
• Hall control unit
• Fuel pump relay
• Oxygen sensor heater
33
Page 38
Digifant
34
Page 39
On Board Diagnostics
Digifant
Golf, Jetta, and Vanagon Digifant systems
have no On Board Diagnostic (OBD) capabilities, except for a limited number of 1987 to
1990 California Golfs and Jettas. These vehicles have blink code capability, with the
capacity to store up to 5 Diagnostic Trouble
Codes (DTCs). For the most part, diagnostic
troubleshooting is done with the VAG 1598
and a digital multimeter. This system can also
have carbon monoxide (CO), ignition timing
and idle speed adjusted to baseline values.
In 1991, California Golf, Jetta, Fox, Cabriolet
and Corrado vehicles were equipped with
expanded OBD capabilities. These latest Digifant versions have 38-pin ECMs with rapid
data transfer and permanent DTC memory. All
Eurovans with Digifant also have rapid data
transfer and permanent DTC memory. These
systems use a throttle plate potentiometer to
track throttle position in place of the idle and
full throttle switches used on earlier systems.
Summary
Digifant is an engine management system
designed originally to take advantage of the
first generation of newly developed digital signal processing circuits. Production changes
and updates were made to keep it current
with the changing California and federal emissions requirements. Updates were also made
to allow integration of other vehicle systems
into the scope of engine operation.
Changes in circuit technology, design and processing speed along with evolving emissions
standards, resulted in the development of
new engine management systems. These
new systems incorporated adaptive learning,
enhanced and expanded diagnostics, and the
ability to meet total vehicle emissions standards.
The table on the following page lists some of
the major differences between versions of
Digifant sold in California and the other states.
35
Page 40
Digifant
36
Page 41
Review
Digifant Review
1. Digifant engine management systems
derive basic fuel injection quantity and
ignition timing points from which two
sensors?
a. Air flow sensor and coolant temper-
ature sensor
b. Knock sensor and camshaft position
sensor
c. Hall sender and coolant tempera-
ture sensor
d. Hall sender and air flow sensor
2. Technician A says that Digifant engine
management systems use digital signal processing for fuel injection control.
Technician B says that Digifant engine
management systems use analog signal processing for ignition control.
Which Technician is correct?
a. Technician A only
b. Technician B only
c. Both Technician A and Technician B
d. Neither Technician A nor Technician
B
3. Which of the following items does not
supply an input to the 25-pin Digifant
control unit?
a. Transmission Control Module (TCM)
b. Air conditioner system
c. Battery voltage
d. Starter
4. Technician A says that the Digifant
ECM operates the fuel injectors by
controlling the ground signal.
Technician B says that the Digifant
ECM operates the fuel pump relay by
controlling the ground signal.
Which Technician is correct?
a. Technician A only
b. Technician B only
c. Both Technician A and Technician B
d. Neither Technician A nor Technician
B
5. Digifant fuel injectors operate:
a. Sequentially every other crankshaft
revolution.
b. At the same time every other crank-
shaft revolution.
c. Sequentially every crankshaft revo-
lution.
d. At the same time every crankshaft
revolution
6. Technician A says that all Digifant
engine management systems use
knock sensors.
Technician B says that all Digifant
engine management systems use idle
and full throttle switches.
Which Technician is correct?
a. Technician A only
b. Technician B only
c. Both Technician A and Technician B
d. Neither Technician A or Technician B
37
Page 42
Notes
38
Page 43
Motronic M2.9 Overview
System description
Motronic M2.9 Overview
Motronic Engine Management was first introduced in combination with the narrow angle
(15°) 2.8 liter VR-6 engine in the 1992 Corrado
SLC. The VR-6 with Motronic was later
installed in the Passat GLX, Golf GTI, Jetta
GLX and Eurovan. Motronic M2.9 engine
management was also installed on Passat and
Golf/Jetta 2.0 liter 4-cylinder 8-valve engines.
The Motronic Engine Management System
combines all fuel, ignition and evaporative
emissions system functions into a single electronic control unit. This electronic control unit
is known as the Engine Control Module
(ECM). The ECM governs all of the output
devices responsible for running the engine,
and operates other related system devices.
Engine-mounted sensors continuously gather
operating data and send this information to
the ECM. This data is converted and processed within the ECM for use in determining
the engine’s momentary operating conditions.
This information is used as the basis for the
ECM’s output signals, and sent to the system
actuators.
As on previous systems, engine management
control is digital electronic, and is based on
engine load and engine speed.
39
Page 44
Motronic M2.9 Overview
Functional overview
Motronic M2.9 uses engine speed and load
as its primary inputs. An inductive sensor
mounted on the cylinder block measures
crankshaft speed, and provides the engine
speed signal.
A Hall sender in the distributor provides camshaft position information to identify cylinder
number one. This allows fuel injection to be
sequential, and timed to the opening of the
intake valve. This is different than previous
systems, in which the injectors all fired at the
same time.
Engine load information is received from the
Mass Air Flow (MAF) sensor G70, which has
no moving parts and is not adjustable.
All Volkswagen engine management systems
with an oxygen sensor adapt to changing conditions while the engine is running. The ECM
uses the oxygen sensor signal to determine
the oxygen content of the exhaust gases. It
then determines if the injector duration needs
to be lengthened or shortened to achieve the
optimum air/fuel ratio of 14.7: 1. This is
referred to as adaptation (see Glossary).
When the ignition is switched off on Digifant
equipped vehicles, all adaptations are erased.
During the time before the oxygen sensor signal is reliable (at operating temperature), the
ECM relies on baseline values from a calculation map. This air/fuel ratio may or may not
reflect the current engine operating conditions because it always represents a basic
setting.
40
Page 45
Motronic M2.9 Overview
Motronic M2.9 engine management systems
take oxygen sensor adaptation to the next
level. Values obtained during engine operation
are stored, and used as the basis for engine
operation on the next start. These stored values are said to be “learned” values and can
change or adapt as often as needed. The process of storing and using learned values is
called adaptive learning (see Glossary).
In addition to mixture adaptation, idle speed
and ignition timing also adapt to changes in
operating conditions (i.e. changes in altitude
and small vacuum leaks). No periodic adjustments are required.
Note:
If the battery is disconnected, or if power is
interrupted to the ECM, all learned or adapted
values will be erased.
The ECM will start from a baseline setting and
relearn and adapt to operating conditions.
With the VAG 1551/1552 or VAS 5051 connected and set to Basic Settings (function 04),
the Motronic system can be made to adapt to
current conditions in several minutes. When
the Basic Settings function is selected the
scan tool instructs the ECM to
• disable the A/C compressor
• disable the EVAP system
• stabilize ignition timing
• stabilize idle speed
Advantages of adaptive learning include:
• optimal fuel economy
• reduced emissions
• reduced maintenance
• improved driveability
Note:
When diagnosing oxygen sensor adaptation
faults, be sure to inspect the following:
• Exhaust system (allows outside air to mix
with exhaust gases and affect oxygen
sensor readings)
• Engine sealing (oil leaks can create false air
leaks when the engine is running, causing
un-metered air to enter the intake manifold)
• False air leaks (can include Idle Air Control
(IAC) valve, or associated intake manifold)
Any of these systems, if not well sealed, can
cause an inaccurate air/fuel mixture, resulting
in poor driveability and possible adaptation
faults.
Always check the basics first!
41
Page 46
Motronic M2.9 Overview
System Adaptation - Balanced
Coarse
100%
Fine
100%
0%
-100%
System Adaptation - Lean
Coarse
100%
0%
-100%
Fine
100%
-100%
Control
Range
SSP 8410/185
Control
Range
The three illustrations show the normal window of operation for an engine management
system, as well as a system that has adapted
to a lean condition and a rich condition.
The layout of the illustrations shows the fine
control range of the fuel system on the right,
with its corresponding position in the coarse
range on the left.
On the balanced system, the fuel trim is in
the center of the graph. This means that the
system has not adapted to any mechanical or
component problems.
The second illustration shows the effect on
the adaptation window from an excess of
unburned Oxygen in the exhaust.
Example:
If a false air leak is introduced, the fuel system
will register a lean running condition. The
Motronic ECM will move the fine control range
from 0% toward 100%, depending on the
severity of the air leak. The system will adapt
and the fine control window will continue to
adjust short term fuel trim accordingly.
-100%
System Adaptation - Rich
Coarse
100%
Fine
0%
-100%
42
100%
-100%
SSP 8410/186
Control
Range
SSP 8410/187
The last illustration shows the system adapting to a rich running condition. This could be
the result of excessive fuel pressure or faulty
injectors, as examples.
Coarse control range is defined as Long term
adaptation or learned value.
Fine control range is defined as Short term
adaptation. Fuel adaptation is the control for
both idle and part throttle conditions.
Idle adaptation is also referred to as:
• Additive
Part throttle adaptation is also referred to as:
• Multiplicative
For definitions, refer to the Glossary.
Page 47
Inputs/Outputs - Motronic M2.9
Motronic M2.9 Overview
The 68-pin ECM used in Motronic M2.9
equipped vehicles receives signals from up to
nine input sources. These include the following:
• Engine Speed (RPM) sensor G28
• Camshaft Position (CMP) sensor G40
• Mass Air Flow (MAF) sensor G70
• Engine Coolant Temperature (ECT) sensor
G62
• Intake Air Temperature (IAT) sensor G42/
G72
• Heated Oxygen Sensor (HO2S) G39
• Throttle Position (TP) sensor G69
• Knock Sensor(s) (KS) G61/G66
• EGR Temperature sensor G98
Additional signals used as inputs include:
• Air conditioner (compressor and/or system
on)
• Battery voltage
• Speedometer Vehicle Speed Sensor (VSS)
G22
• Transmission Control Module (TCM) J217
ECM output to actuators controlling engine
operation include:
• Fuel injectors N30-N33,N83,N84
• Idle Air Control (IAC) valve N71
• Ignition Coil Power Output Stage N157
• Fuel Pump (FP) relay J17
• Heated Oxygen sensor (HO2S) control
module J208.
• Heated Oxygen sensor (HO2S) relay J278
• EGR vacuum regulator solenoid valve N121/
N18
• Evaporative Emissions (EVAP) Canister
Purge Regulator Valve N80
• Secondary Air Injection (AIR) solenoid valve
N112
• Secondary Air Injection (AIR) pump motor
V101
Several other systems require input from the
Motronic M2.9 system, or provide input to
alter the engine management.
The Transmission Control Module (TCM)
requires data corresponding to throttle position, engine load, and engine RPM for shift
control. The TCM uses these inputs to control
upshifts as well as downshifts according to
driving conditions. The TCM also sends a shift
“signal” to the ECM, the ECM retards ignition
timing during the shift to help “soften” the
shift.
Sensor inputs, other input signals, actuator
signals and other output signals are shown in
the illustration on the following pages. The
illustration represents a composite view of
components that are installed on several different engine types. Components listed may
not be applicable to all engines.
43
Page 48
Motronic M2.9 Overview
44
Page 49
Motronic M2.9 Overview
45
Page 50
Motronic M2.9 Overview
On-Board Diagnostics
Motronic M2.9 engine management systems
comply with the On-Board Diagnostic standards for OBD I, including:
• Diagnostic Trouble Code (DTC) retrieval via
blink code
• VAG 1551/1552 and VAS 5051 scan tool
support for Rapid Data Transfer
• Diagnosis of open/short circuits for most
sensors and actuators
Rapid data supported functions include:
• Retrieval and erasing of DTCs
• ECM identification and coding
• Viewing and setting of engine operating
data
• Actuator function testing
Signal usage
The following table summarizes the usage
and function of Motronic M2.9 input signals
found on early VR-6 engines.
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Motronic M2.9 Component
Summary
Fuel system components
Motronic M2.9 Component Summary
Fuel tank
Motronic equipped vehicles all use an injection molded plastic fuel tank located at the
center-rear of the vehicle. The fuel tank
assembly includes the filler neck and all of the
fuel vent system. The fuel tank has an opening in the top large enough to allow placement of the fuel delivery unit within the tank.
The delivery unit includes the fuel pump
assembly, the fuel gauge sending unit, the
fuel feed and return lines, and all the electrical
connectors.
A large capacity fuel filter is mounted close to
the tank in the fuel line feeding the engine.
Fuel Pressure Regulator
The fuel pressure regulator is a diaphragmtype regulator attached to the fuel manifold
on the return, or outlet side. Fuel pressure is
regulated by controlling the fuel returned to
the tank and is dependent on intake manifold
pressure (engine load).
As intake manifold pressure changes, the
pressure regulator will increase or decrease
the system fuel pressure. This maintains a
constant pressure difference between the
injector outlet which is within the intake manifold and the injector inlet which is exposed to
fuel pressure.
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Motronic M2.9 Component Summary
Engine Control Module (ECM) J220
The ECM must be supplied with the appropriate power sources and Grounds to function
properly. Additionally, the ECM must “know”
what equipment is installed in the vehicle.
This process is known as coding, and must
be performed whenever the ECM is replaced.
New ECMs are generally shipped un-coded.
Coding memory is retained when the battery
is disconnected. If a new ECM is installed
without being coded, the engine may run
poorly and the automatic transmission (if
equipped) will not function properly. The ECM
is electronically coded using the scan tool.
ECU part
number
The ECM is equipped with rapid data transfer
to facilitate communication with either the
VAG 1551/VAG 1552 scan tools or the VAS
5051 Diagnostic Testing and Information System for retrieval of system and component
malfunctions. System operating information
can be viewed in real time as an aid in diagnosis.
System
type
Software
version
Engine
coding
48
Workshop
code
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Motronic M2.9 Component Summary
Input sensors
Motronic engine management systems rely on up to nine different input sensors for engine
operating information. Different Motronic versions have variations of some sensors, but the signal usage and component operation remains essentially the same.
Mass Air Flow (MAF) sensor G70
Two versions of the mass air flow sensor are
used on Volkswagen Motronic engine management systems; hot wire and hot film.
A hot-wire mass air flow sensor was used
on VR-6 Motronic M2.9 engines from model
years 1992 to 1994.
The mass air flow sensor is mounted to the
air filter housing and measures air flow into
the engine (which is an indication of engine
load). A velocity stack is built into the air filter
housing to shape and direct the incoming air
charge, and a baffle reduces air turbulence
and pulsing before measurement.
A thin electrically-heated, platinum hot-wire in
the sensor is kept 180°C (356°F) above the air
temperature as measured by the built-in thinlayer platinum air temperature sensor.
As air flow increases, the wires are cooled
and the resistance of the sensors changes.
Electrical current to the platinum hot-wire varies to maintain the constant temperature difference. The resulting current change is
converted to a voltage signal, and is used by
the ECM to calculate the mass of air taken in.
Dirt or other contamination on the platinum
wire can cause inaccurate output signals.
Because of this, the platinum wire is heated
to approximately 1000°C (1832°F) for a period
of one second each time the engine is
switched off (after being run to operating temperature). This burns off any dirt or contamination.
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Motronic M2.9 Component Summary
A hot film mass air flow sensor was
installed on Passat VR-6 Motronic M2.9
engines from model year 1995; Golf/Jetta VR6 Motronic M2.9 engines from 1994; Golf/
Jetta/Cabrio 4-cylinder M2.9 engines from
1993; and Passat 4-cylinder M2.9 engines
from 1995. It is mounted in the same location
as the hot-wire version.
The hot film mass air flow sensor uses a
heated metallic film on a ceramic substrate
instead of the hot-wire. The film is kept at a
constant temperature above the intake air
temperature by varying the current in much
the same way as the hot-wire version.
This sensor differs from the hot-wire mass air
flow sensor used earlier, because it does not
require the “burn-off” phase to clean the sensor after the engine is switched off.
• Operation:
Air flows past the hot film and cools it.
Current is supplied to maintain constant
temperature. Changing current is converted to a signal used by the ECM to
determine engine load.
• Substitute function:
If a fault develops with the signal from
the mass air flow sensor, the signal from
the throttle position sensor potentiometer is used as a substitute. Driveability is
maintained and a fault or Diagnostic Trouble Code (DTC) is stored in the ECM.
• On Board Diagnostic (OBD):
The ECM recognizes open circuits and
short circuits and sets an appropriate
DTC.
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Motronic M2.9 Component Summary
Throttle Position (TP) sensor G69
The throttle position sensor is a potentiometer connected to the throttle valve shaft. The
signal generated is used by the ECM to determine driver input.
Idle and full throttle switches are not incorporated into the throttle position sensor. These
positions are recognized by the ECM from the
appropriate voltage output of the potentiometer. Throttle position sensor signals are used
by the ECM for determination of idle speed
stabilization, idle air volume control, deceleration fuel shut-off, acceleration and full load
enrichment.
Vehicles with electronically controlled automatic transmissions also require a throttle
position sensor signal. This signal comes
either from a second throttle position sensor
or from the ECM, and is passed on to the
Transmission Control Module (TCM).
• Operation:
The ECM supplies a fixed voltage signal
to the throttle position sensor. Movement
of the throttle valve rotates a potentiometer, varying the resistance (voltage drop
changes). The signal is then sent to the
ECM.
• Substitute function:
If a fault develops with the signal from
the throttle position sensor, the signals
from the mass air flow sensor and the
engine speed (RPM) are used as a substitute. Driveability is maintained and a fault
or Diagnostic Trouble Code (DTC) is
stored in the ECM.
• On Board Diagnostic (OBD):
The ECM recognizes open circuits and
short circuits.
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Motronic M2.9 Component Summary
Engine Speed (RPM) sensor G28
Engine speed and crankshaft position are registered by a single sensor located on the
engine cylinder block. The sensor reads a
toothed wheel mounted on the crankshaft
through a hole in the lower part of the cylinder
block.
The toothed wheel has space for 60 teeth. A
two-tooth gap is used as a reference for
crankshaft position.
The engine speed (RPM) sensor G28 signal is
used for registration of engine speed. It is
used in conjunction with the signal from the
camshaft position sensor to identify cylinder
number 1 for sequential fuel injection and cylinder selective knock control. The ECM also
sends engine speed information from this
sensor to all other systems that require it,
such as the Transmission Control Module
(TCM) and the instrument cluster.
• Operation:
The Engine Speed (RPM) sensor G28 is
an inductive sensor. The rotating sensor
wheel causes an alternating current signal to be generated whose frequency
varies with engine speed. The gap
causes a slight variance in the pulses and
identifies crankshaft position.
• Substitute function:
There is no substitute function for the
speed/reference sensor. The engine will
not start or run.
• On Board Diagnostic (OBD)
The ECM recognizes open circuits, and
incorrect signals in this component and
sets an appropriate DTC. This component
will always show a DTC if the ECM fault
memory is checked with the ignition on,
but the engine not running. It will automatically erase itself when the engine
starts.
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Motronic M2.9 Component Summary
Camshaft Position (CMP) sensor G40
Two major types of camshaft position sensors
are used on Volkswagen Motronic engine
management systems. The type is dependent
upon whether or not the engine uses a distributor, or is distributor-less.
Engines that use distributors mount the Camshaft Position (CMP) sensor in the distributor
housing. A shutter wheel with a single cut-out
is attached to the distributor shaft.
Engines with distributor-less ignitions mount
the camshaft position sensor to the end of
the cylinder head where the shutter wheel is
driven directly by the camshaft.
The camshaft position sensor is a Hall sender
(see Glossary). It is housed in plastic to protect it from moisture, dirt, oil, and mechanical
damage.
The camshaft position sensor signal is used
along with the engine speed (RPM) sensor to
identify cylinder number 1 for purposes of
sequential fuel injection and knock regulation.
Engine Speed (RPM) sensor G28
1
Cam Position (CMP) sensor G40
(with reference mark)
3 2 1
4
SSP 8410/182
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Motronic M2.9 Component Summary
• Operation:
The ECM supplies a fixed voltage signal
to the camshaft position sensor. An on/
off voltage signal is generated and
returned to the ECM when the rotating
shutter wheel interrupts the magnetic
field generated by the Hall effect semiconductor. One signal is generated for
every two crankshaft revolutions.
Note:
It is important for the ECM to receive the
Camshaft Position (CMP) sensor signal in
phase with the Engine Speed (RPM) sensor signal. If not, the ECM will record an
open/short circuit to Battery + DTC,
despite the fact that the sensors are
working correctly.
• Substitute function:
There is no substitute function for the
camshaft position. If a fault develops with
the signal from the camshaft position
sensor, the ECM will revert to nonsequential injection and retarded, noncylinder selective knock control. Engine
output is reduced, and a fault or Diagnostic Trouble Code (DTC) is stored in the
ECM.
• On Board Diagnostic (OBD):
The ECM recognizes open circuits and
short circuits.
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Motronic M2.9 Component Summary
Knock Sensor (KS) I G61 and Knock Sensor
(KS) II G66
A knock sensor is a piezo-electric device that
works like a sensitive microphone to detect
vibrations in an engine. Since certain types of
vibrations are associated with engine knock, a
knock sensor provides a means for the ECM
to monitor the combustion process. The purpose of the knock sensor is to keep combustion at the very edge of knock.
A single knock sensor monitors all cylinders
on 4-cylinder engines and is centrally
mounted on the lower front area of the cylinder block. Dual knock sensors are used on the
VR-6-cylinder engines with sensor I responsible for cylinders 1, 3, and 5, and sensor II
responsible for cylinders 2, 4, and 6. Knock
sensor I is mounted to the rear of the cylinder
block and knock sensor II is mounted to the
front.
Knock Sensors
(G61, G66)
SSP 8410/82
Knock sensors must be correctly torqued to
the cylinder block in order to function properly. Correct torque pre-loads the sensor,
allowing for proper operation.
When the knock sensor detects vibrations
over and above a specified background level
of noise, the individual cylinder is identified
with the help of the camshaft position sensor.
The ignition timing point for that particular cylinder is then retarded by a pre-determined
amount until the knocking is eliminated.
Once the knocking stops, the ECM advances
the timing in smaller steps until it returns to
the programmed point, or until it knocks
again. If knocking re-occurs, the process is
repeated.
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Motronic M2.9 Component Summary
Differences between individual cylinder timing cannot exceed 12°. If the timing for an
individual cylinder reaches 12° and it continues to knock, all remaining cylinders are
retarded by 11° (even if they are not knocking), and a DTC is recorded.
Knock regulation does not occur until engine
coolant temperature is above 40°C (104°F).
• Operation:
When subjected to engine vibration, the
knock sensor generates its own continuous small voltage signal. The presence of
knock changes the signal. The ECM identifies the change in signal voltage as
engine knock.
• Substitute function:
There is no substitute function. However,
if a sensor fails, the timing of its assigned
cylinders is retarded.
• On Board Diagnostic (OBD):
The ECM recognizes open circuits and
short circuits from the knock sensor(s) if
no signal is received at coolant temperatures over 40°C (104°F).
Note:
Knock Sensor mounting torque is critical for
proper operation. Always refer to appropriate
Service Information for latest specifications.
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Motronic M2.9 Component Summary
Heated Oxygen Sensor (HO2S) G39
The heated oxygen sensor is constructed of
the ceramic material zirconium dioxide and is
stabilized with yttrium oxide. It is mounted in
the exhaust stream close to the engine. The
inner and outer surfaces of the ceramic material are coated with platinum. The outer platinum surface is exposed to the exhaust gas,
while the inner surface is exposed to the outside air.
The difference in the amount of oxygen contacting the inner and the outer surfaces of the
oxygen sensor creates an electrical pressure
differential, resulting in the generation of a
small voltage signal. This voltage falls within
the range of 100 mV to 1000 mV. The exact
voltage depends on the oxygen levels present
in the exhaust gas and is a result of the air/
fuel mixture.
1000mV
450mV
λ
window
{
Oxygen sensors in earlier systems were
heated by exhaust gas. The oxygen sensor is
now heated electrically to keep it at a constant operating temperature. The heater also
insures that the sensor reaches operating
temperature quickly and remains there.
• Operation:
The base fuel injection opening time is
modified according to the voltage signal
from the oxygen sensor to maintain an
air/fuel ratio of approximately 14.7:1. This
mixture ratio is known as lambda (λ).
This optimal mixture of 14.7:1 is referred
to as “lambda of 1 (λ=1)” and allows the
three-way catalytic converter to operate
at its maximum efficiency.
If the air/fuel mixture is lean (excess oxygen), the voltage signal sent to the ECM
will be low (approximately 100 mV). This
is because the voltage difference
between the inner and outer surfaces of
the ceramic material is low; low differences equate to low voltages.
0mV
Rich
λ
Lean
SSP 8410/198
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Motronic M2.9 Component Summary
If the air/fuel mixture is rich (lacking oxygen), the voltage signal sent to the ECM
will be high (approximately 900 mV). This
is because the voltage difference
between the inner and outer surfaces of
the ceramic material is high; high differences equate to high voltages.
Oxygen sensors usually have four wires
plus a separate grounded shield wire.
The signal wire and a dedicated Ground
wire are contained within the grounded
shielding wire. Individual power and
Ground wires are provided for the heating element. Additionally, the sensor is
grounded when threaded into place.
The period of time after an engine start
when the oxygen sensor is not at operating temperature, and therefore not used,
is called open loop operation. This condition can occur after either a cold or
warm start. Conversely, engine operation
with a valid oxygen sensor signal is called
closed loop operation.
As a result of the HO2S signal, the ECM
lengthens the injector duration to richen
the mixture, and shortens the duration to
lean it out.
• Substitute function:
There is no direct substitute function for
the oxygen sensor. If the sensor malfunctions, no oxygen sensor regulation will
occur. The ECM will, however, revert to
the base fuel injection opening time,
allowing the engine to continue to run.
• On Board Diagnostic (OBD):
The ECM recognizes malfunctions in the
oxygen sensor signal if no plausible signal is received within approximately five
minutes after an engine start with coolant temperature over 40°C (104°F). It also
recognizes open circuits and short circuits.
The ECM uses a correctly operating oxygen sensor to monitor faults with mixture
control and other systems that influence
mixture.
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Motronic M2.9 Component Summary
Engine Coolant Temperature (ECT) sensor
G62
The engine coolant temperature sensor is an
NTC sensor (see Glossary), mounted in the
coolant flow near the cylinder head. As
engine coolant temperature changes, the
resistance of the sensor changes, providing
the ECM with engine temperature data.
Coolant temperature sensor signal data is
used as a correction factor for determining
ignition timing, injector duration, and idle
speed stabilization. In addition, several other
systems or functions depend on coolant temperature sensor data for activation. These systems include:
• Knock sensor function
• Idle speed adaptation
• Oxygen sensor operation
SSP 8410/75
• Fuel tank ventilation
For identification purposes, the coolant temperature sensor housing is usually blue in
color, and is usually combined in the same
housing as the Engine Coolant Temperature
(ECT) sensor G2, which is used for the coolant
gauge in the instrument cluster.
• Operation:
The ECM supplies a fixed reference voltage signal to the coolant temperature
sensor and monitors the voltage drop
caused by the resistance change.
Increasing (warmer) temperatures cause
the resistance to decrease; decreasing
(colder) temperatures cause the resistance to increase.
• Substitute function:
If a fault develops with the coolant temperature sensor, the ECM substitutes a
value equivalent to 80°C (176°F).
• On Board Diagnostic (OBD):
The ECM recognizes open circuits and
short circuits.
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Motronic M2.9 Component Summary
Intake Air Temperature (IAT) sensor G42 or
G72
The intake air temperature sensor is also an
NTC sensor (see Glossary), and is mounted in
the intake manifold. As incoming air for combustion flows past the sensor, the resistance
of the sensor changes, providing the ECM
with air temperature data.
Intake air temperature sensor signal data is
used as a correction factor for ignition timing
and idle speed stabilization.
• Operation:
SSP 8410/73
The ECM supplies a fixed reference voltage signal to the intake air temperature
sensor and monitors the voltage drop
caused by the resistance change.
Increasing (warmer) temperatures cause
the resistance to decrease; decreasing
(colder) temperatures cause the resistance to increase.
• Substitute function:
If a fault develops with the intake air temperature sensor, the ECM ignores the
sensor and substitutes a value equivalent
to 20°C (68°F) from memory.
• On Board Diagnostic (OBD):
The ECM recognizes open circuits and
short circuits.
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Motronic M2.9 Component Summary
Exhaust Gas Recirculation (EGR)
temperature sensor G98
Depending on the vehicle type and the marketing area, some vehicles are equipped with
exhaust gas recirculation. The EGR system
takes a small part of the non-combustible
exhaust gas and injects it back into the intake
tract to take up a small amount of space in
the incoming air charge. The result is lower
combustion temperatures and reduced oxides
of Nitrogen (NO
The Exhaust Gas Recirculation (EGR) temperature sensor is an NTC sensor (see Glossary)
mounted in the EGR valve. When the EGR is
enabled by the ECM, the EGR valve opens,
allowing the hot exhaust gases to flow past
the temperature sensor. This raises the temperature substantially, changing the resistance of the sensor and providing the ECM
with confirmation of EGR operation.
• Operation:
).
X
The ECM supplies a fixed reference voltage signal to the EGR temperature sensor and monitors the voltage drop caused
by the resistance change. Increasing
(hotter) temperatures cause the resistance to decrease; decreasing (cooler)
temperatures cause the resistance to
increase.
• Substitute function:
There is no substitute function.
• On Board Diagnostic (OBD):
The ECM recognizes short circuits.
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Motronic M2.9 Component Summary
Additional input signals
Several other signals are used by the ECM in much the same manner as input sensors.
Depending on installed vehicle equipment, these additional signals may include:
• Battery voltage:
Aside from the voltage needed to actually
operate the Motronic engine management system, the ECM monitors voltage
to compensate for the quicker operation
of some components due to higher or
lower available operating voltage. Fuel
injectors, for example, cycle slightly
faster at 14.5 Volts than they do at 12
Volts or lower. This faster cycle time
must be figured into the calculation of
duration for accuracy.
• Air conditioner “System ON” signal:
The air conditioner system signal allows
the ECM to be prepared for the additional
load demands of the air conditioner on
the engine.
• Air conditioner compressor “Clutch ON”
signal:
The compressor “clutch on” signal prepares the ECM for a quick response to
the sudden engine speed changes that
occur when the compressor clutch is
engaged, particularly at idle.
• Vehicle speed sensor signal:
The vehicle speed sensor signal originates from the instrument cluster and is
used by the ECM to control the idle stabilizer during deceleration, and to limit vehicle top speed.
• Automatic Transmission Control Module
(TCM) signal:
The TCM sends a signal to the ECM during shifting. This allows the ECM to
retard ignition timing for smoother shifting.
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Motronic M2.9 Component Summary
Actuators (outputs)
Motronic engine management systems rely on different actuators to run the engine and operate related systems. The type and number of actuators varies with the Motronic version, but
the basic operation remains essentially the same for all versions.
Cylinders 1 - 4 fuel injectors N30 - N33
Cylinders 5 - 6 fuel injectors N83 - N84
Motronic fuel injectors are electronically controlled solenoid valves (see Glossary).
Fuel injectors are attached to a common fuel
rail with locking clips, and sealed at both ends
by serviceable O-rings. The fuel rail doubles
as a retaining bracket.
Fuel injector internal resistance specifications
vary slightly depending on application, but
typically are in the area of 15 Ohms. It should
be noted that higher temperatures will cause
resistance values to increase.
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Motronic M2.9 Component Summary
• Operation:
The fuel injectors are supplied with constant system voltage by a supply relay,
and are triggered in firing order sequence
when the ECM supplies a Ground signal.
When the injector opens, a fine spray of
fuel is mixed with the incoming air flow.
The volume or quantity of fuel is determined by the length of time that the
ECM supplies the Ground signal. The
longer the signal, the greater the fuel
delivery. The time period is called injec-
tor duration.
Fuel injectors are switched off during certain phases of normal engine operation.
When the engine is running at higher
speeds with a closed throttle such as
when “coasting,” the ECM switches off
the injectors to reduce emissions (deceleration fuel shut-off). Fuel injectors are
also switched off at high engine speeds to
limit maximum RPM.
• On Board Diagnostic (OBD):
The ECM recognizes open circuits and
short circuits. Additional diagnostic testing is available with the scan tool set in
the output Diagnostic Test Mode (DTM).
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Ignition coil N152
Power output stage N157
Motronic M2.9 Component Summary
The ignition power output stage is mounted
to the ignition coil and amplifies the low
power signal from the ECM to a usable level.
The ignition coil is a type of step-up transformer that takes the low primary voltage and
raises it to the high secondary voltage level
required by the spark plugs to ignite the mixture within the cylinder (see Ignition System
Overview).
The combined ignition coil and power output
stage is mounted to either the engine itself or
the bulkhead. In some Motronic versions, the
power output stage can be separated from
the ignition coil for testing, but the power output stage and the ignition coil are only serviceable as a complete assembly.
• Operation:
The ignition system is triggered and the
spark plugs fire when the ECM supplies a
signal to the power output stage. This
signal is primarily based on engine speed
and load inputs.
Correction factors from other relevant
input sensors allow the trigger signal
generated to provide the correct ignition
timing advance.
Additional ECM calculations include:
• dwell angle
• cylinder selective knock regulation
• Idle Speed Control (ISC) (see Glossary)
The power output stage and coil are supplied
with power and Ground when the ignition is
switched on. Systems with a distributor
charge the ignition coil every time the spark
plug fires. Systems without a distributor use
multiple coils. The VR-6, for example, uses
three double-ended coils with a spark plug
attached to each end. At every firing pulse,
when the magnetic field collapses, both spark
plugs fire. The only cylinder to fire, however,
is the one coming up on the compression
stroke. The other spark occurs when the cylinder is not ready to be fired, and is considered to be a wasted spark. Since this spark
does not ignite a combustible mixture, and is
not under the severe heat and pressure of
combustion, it causes no appreciable wear on
the spark plug.
• On Board Diagnostic (OBD):
The ECM recognizes short circuits to Battery (+) positive.
SSP 8410/65
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Motronic M2.9 Component Summary
Fuel Pump (FP) relay J17
Fuel Pump (FP) G6
Motronic engine management systems use a
fuel tank-mounted two-stage electric fuel
pump controlled by a signal from the ECM
through the fuel pump relay. Mounting the
pump within the fuel tank keeps the pump
continuously cooled and lubricated by the circulating fuel. The fuel also provides sound
absorption, resulting in quieter operation.
• Operation:
When the ECM determines that the
appropriate conditions have been met, a
Ground signal is sent to the fuel pump
relay. This relay operates the two-stage
electric fuel pump mounted in the fuel
tank.
The two-stage fuel pump has a single
electric motor driving two separate
pumps on a common shaft.
• Stage One
Fuel is drawn in through a screen at the
bottom of the housing assembly by a
vane-type pump. The screen provides
coarse filtration, and the vane-type pump
acts as a transfer pump. Its high volume
design supplies fuel to the fuel accumulator which is within the pump housing.
• Stage Two
The gear-type pump draws fuel in from
the bottom of the accumulator and
through another screen. The fuel is then
forced through the pump housing by the
gear pump and out through the top of the
fuel tank. It then flows through the external fuel filter and into tubes that carry it
forward to the engine.
• On Board Diagnostic (OBD):
The ECM recognizes fuel pump relay
short circuits to positive. Additional diagnostic testing is available using the scan
tool set in the output Diagnostic Test
Mode (DTM).
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Motronic M2.9 Component Summary
Idle Air Control (IAC) valve N71
Engine idle speed is controlled by a rotaryvalve idle stabilizer known as an idle air control valve. Because the valve varies the volume of air that is allowed to bypass the
closed throttle valve, it is mounted near the
throttle housing. Idle speed control (ISC) from
the ignition system also helps to provide a
smooth idle.
Load changes, such as those imposed by air
conditioning, power steering, the generator,
or a cold engine can cause the idle speed
requirement to vary considerably. The idle air
control valve opens or closes under the control of the ECM to maintain a constant idle
speed regardless of temperature or load.
The ECM also controls the air flow during
engine and vehicle deceleration to minimize
emissions and reduce stalling tendencies. It
does this by operating the idle air control
valve as an electronic dashpot (see Glos-
sary).
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Motronic M2.9 Component Summary
The idle air control valve is not adjustable.
• Operation:
The idle air control valve housing mounts
an electric motor with 90° of rotation.
Attached to the motor shaft is a rotary
valve and a return spring. When the ECM
commands more throttle opening, more
power is sent to the motor, opening the
valve against spring tension. When less
speed is required, the power is reduced.
The valve closes against spring tension
reducing the air flow and dropping the
speed.
• Substitute function:
If a fault develops with the idle air control
valve circuitry, the ECM output stages
are shut off and the valve rotates to a
fixed position allowing the engine to idle
at a normal warm engine idle speed.
• On Board Diagnostic (OBD):
The ECM recognizes open circuits and
short circuits to Ground and Battery +, as
well as adaptation limit reached/
exceeded and sets an appropriate DTC.
Additional diagnostic testing is available
using the scan tool in the output Diagnostic Test Mode (DTM).
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Motronic M2.9 Component Summary
Evaporative Emission (EVAP) canister
purge regulator valve N80
The fuel tank ventilation system is designed
to prevent fuel vapors from escaping directly
to the atmosphere. Purging of fuel vapors
from the fuel system is controlled by the ECM
working via the evaporative emissions solenoid valve located near the engine air intake.
Fuel vapors from the fuel tank are vented to
the carbon canister for storage. When the
engine is warm and above idle speed, the
vapors are drawn into the intake manifold via
the tank vent hose and the carbon canister.
• Operation:
The ECM determines the duty cycle of
the frequency valve to regulate the flow
of the fuel vapors from the carbon canister to the engine.
A spring operated check valve inside the
frequency valve closes when the engine
is not running. This prevents fuel vapors
from entering the intake manifold and
causing an excessively rich mixture on a
restart. When the engine is started, vacuum opens this valve.
When no current is supplied to the valve,
it remains in the open position. The valve
is closed (duty cycle = 100%) when the
cold engine is started.
N80 begins to operate after oxygen sensor operation has begun. Depending on
engine load and the oxygen sensor signal, the evaporative emissions solenoid
valve will regulate the quantity of vapors
entering the intake manifold from the carbon canister. The valve is completely
open at full throttle, and completely
closed during deceleration fuel shut-off.
• Substitute function:
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Motronic M2.9 Component Summary
If power to the valve is interrupted, the
valve remains fully open (as long as vacuum is applied to the check valve).
• On Board Diagnostic (OBD):
The ECM recognizes open circuits and
short circuits in this component and sets
an appropriate Diagnostic Trouble Code
(DTC). Additional diagnostic testing is
available with the scan tool set in the output Diagnostic Test Mode (DTM).
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Motronic M2.9 Component Summary
Exhaust Gas Recirculation (EGR)
vacuum regulator solenoid valve N18
Exhaust Gas Recirculation (EGR) is the process by which a small amount of the spent
combustion gas is re-injected into the intake
air tract to be mixed with the fresh air/fuel
charge and be reburned. Since there is very
little combustibility left in the injected gas, it
simply occupies space and reduces combustion chamber temperatures which, in turn,
reduces harmful emissions of oxides of nitrogen (NO
The EGR vacuum regulator solenoid valve is
mounted on the rear of the intake manifold
(close to the EGR valve) and regulates the
amount of vacuum supplied to the EGR valve
(which regulates the amount of EGR).
• Operation:
).
X
A controlling pressure (vacuum) is
formed in the regulator valve from intake
manifold pressure (vacuum) and atmospheric pressure. The atmospheric pressure is taken from a filtered air source.
The ECM operates the regulator valve by
supplying an appropriate Ground signal.
The regulator valve then controls the
amount of vacuum supplied to the EGR
valve diaphragm by cycling between the
connection to the EGR valve and the
atmospheric vent.
The actual amount of recirculated
exhaust gas entering the engine is calculated by the ECM, and is dependent on
engine speed and load conditions. The
maximum vacuum supplied to the EGR
valve is limited to approximately 200
mbar by a membrane valve within the
solenoid valve.
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Motronic M2.9 Component Summary
• Substitute function:
There is no substitute function for the
EGR vacuum regulator solenoid valve. If
no vacuum is supplied to the EGR valve,
it will remain in the closed or off position.
• On Board Diagnostic (OBD)
The ECM monitors the EGR solenoid
valve for open circuits and short circuits.
It also monitors EGR valve operation via
the EGR temperature sensor. Additional
diagnostic testing is available with the
scan tool set in the output Diagnostic
Test Mode (DTM).
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Secondary Air Injection (AIR)
solenoid valve N112
pump motor V101
pump relay J299
Motronic M2.9 Component Summary
Most VR-6 engines and some 4-cylinder
engines use an electrically operated air pump
to reduce exhaust emissions during engine
warm-up.
After a cold engine start, when the heated
oxygen sensor signal is not accurate, the
engine management system is in open loop
mode. The secondary air injection system
adds extra air into the exhaust stream just
past the exhaust valves to aid in the afterburning of the combustion gases.
Advantages to this function include:
• Quicker warm-up for the three-way catalytic
converter and heated oxygen sensor.
• Air/fuel ratios that make this process work
most efficiently also improve driveability.
• Exhaust emissions are reduced.
Secondary air injection system electrical components include an air pump, a solenoid valve,
and a relay. A mechanical shut-off valve and
connecting pipes complete the major system
components.
• Operation:
When the engine is first started and the
coolant temperature is between 15°C
(59°F) and 35°C (95°), the ECM signals
the relay which operates the secondary
air injection pump and solenoid inlet
valve. The air pump runs and the solenoid
inlet valve opens. This sends vacuum to
the shut-off valve, opening it. The pump
then forces a calibrated amount of air into
each exhaust port where it mixes with
any unburned fuel to continue the combustion process. Operation continues for
up to 65 seconds; the pump stops, and
the shut-off valve closes. The additional
heat generated by this process allows
the three-way catalytic converter to reach
operating temperature faster.
SSP 8410/44
Approximately 15 seconds after the air
pump switches off, the system will
momentarily cycle on again, sending a
blast of air past the oxygen sensor. The
ECM anticipates the sudden change in
the oxygen sensor signal that accompanies the system being switched on, and
does not change the mixture. Rather, it
uses this to confirm proper secondary air
injection system operation to the ECM.
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Motronic M2.9 Component Summary
74
• Substitute function:
There is no substitute function for the
secondary air injection system. If no vacuum is supplied to the shut-off valve, it
will remain in the closed or off position.
• On Board Diagnostic (OBD)
The ECM recognizes short circuits to Battery +, and open and short circuits to
Ground for both the Secondary Air Injection (AIR) relay and the Secondary Air
Injection (AIR) solenoid valve. Additional
diagnostic testing is available with the
scan tool set in the output Diagnostic
Test Mode (DTM).
SSP 8410/45
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Motronic M2.9 Component Summary
Heated Oxygen Sensor (HO2S)
Control Module J208
Heated Oxygen Sensor (HO2S)
relay J278
The oxygen sensor heater helps to bring the
oxygen senor up to operating temperature
quickly. The ECM controls the oxygen sensor
heater through either a relay or a control module.
• Operation:
The ECM receives the appropriate input
signals and when the engine is started, a
signal is sent to the oxygen sensor
heater relay or control module. This puts
the engine management system into
closed loop operation sooner.
• Substitute function:
There is no substitute function for a malfunctioning oxygen sensor heater control
module.
• On Board Diagnostic (OBD)
The ECM recognizes short circuits to
positive and open and short circuits to
Ground. Additional diagnostic testing is
available with the scan tool set in the output Diagnostic Test Mode (DTM).
Malfunction Indicator Light (MIL)
Motronic engine management systems are
capable of sending a signal to a warning light
if malfunctions occur with monitored components. The MIL is located within the instrument cluster.
• On Board Diagnostic (OBD)
The ECM recognizes short circuits to
positive and open and short circuits to
Ground with the MIL circuit.
80
60
40
20
10
mph
CHECK
100
140
120
20
10
CHECK
40
30
50
60
70
SSP 8410/46
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Motronic M2.9 Component Summary
Additional output signals
The ECM generates several output signals that are used by other vehicle systems. These signals are derived from input sensors or internal ECM calculations, and usage varies with the
equipment installed on the vehicle.
• Engine speed signal:
The ECM generates an engine speed or
RPM signal that is sent to several other
systems.
The instrument cluster uses the RPM signal for tachometer operation and dynamic
oil pressure warning.
The Transmission Control Module (TCM)
uses the RPM signal as a substitute function for a missing transmission vehicle
speed sensor signal.
• Engine load signal:
The ECM generates a composite load
signal used by the multi-function indicator (MFI) for miles-per-gallon calculations
on vehicles equipped with the MFI.
The ECM monitors this function and rec-
ognizes short circuits to positive.
• Throttle position:
Early Motronic vehicles equipped with
automatic transmissions used separate
throttle position sensors for the engine
and the transmission control modules.
However, later versions use a single TPS,
and pass the throttle opening information
to the TCM through the ECM.
The ECM monitors this function and recognizes short circuits to Ground.
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Review
Motronic M2.9 Review
1. Which of the following components
does NOT receive an output signal
from the Motronic M2.9 engine management system ECM?
a. Idle air control valve (IAC)
b. Fuel injectors
c. Fuel pump relay
d. Intake air pre-heat servo
2. Technician A says that Motronic M2.9
engine management systems can
adapt to variables such as small vacuum leaks and altitude.
Technician B says that Motronic M2.9
engine management systems require
periodic manual carbon monoxide
(CO) adjustments.
Which Technician is correct?
a. Technician A only
b. Technician B only
c. Both Technician A and Technician B
d. Neither Technician A nor Technician
B
3. Motronic M2.9 engine management
systems store and use learned values.
This process is called:
a. Stoichiometric
b. Adaptive learning
c. Lambda
d. Default value retention
4. Technician A says that the Motronic
M2.9 ECM retains learned values when
the battery is disconnected.
Technician B says that the Motronic
M2.9 ECM combines all fuel and ignition functions, but uses a separate
ECM for evaporative emissions and
secondary air injection operation.
Which Technician is correct?
a. Technician A only
b. Technician B only
c. Both Technician A and Technician B
d. Neither Technician A nor Technician
B
5. Motronic M2.9 fuel injectors operate:
a. Sequentially
b. In groups of two
c. All at the same time
d. None of the above
6. Technician A says that all Motronic
M2.9 engine management systems
use exhaust gas recirculation.
Technician B says that all Motronic
M2.9 engine management systems
use secondary air injection.
Which Technician is correct?
a. Technician A only
b. Technician B only
c. Both Technician A and Technician B
d. Neither Technician A nor Technician
B
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Motronic M2.9 Review
7. Which of the following statements is
NOT applicable to the Motronic M2.9
engine management system?
a. Fuel injection control is digital elec-
tronic.
b. All versions are capable of commu-
nicating with scan tools VAG 1551/
1552 and VAS 5051.
c. The ECM can communicate with
the TCM if the vehicle is equipped
with an automatic transmission.
d. Ignition timing, idle speed and mix-
ture adjustments should not be
required until 30,000 miles (48,000
km).
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Mono-Motronic System Overview
System Description
Mono-Motronic
Beginning with the 1993 model year, Canadian base model Golf CLs were equipped
with a 1.8 liter engine with Mono-Motronic
Engine Management.
Mono-Motronic engine management combines familiar Digifant system elements with
Motronic M2.9 system elements. Several
new functions are combined with throttlebody fuel injection to complete the system.
Mono-Motronic engine management controls the following engine functions:
• Fuel injection quantity
• Ignition timing
• Fuel tank ventilation
• Idle speed stabilization
Fuel injection control is electronic. It is based
on the quantity of air entering the throttle
body as indicated by the throttle valve position
sensor. The throttle valve position sensor’s
dual potentiometers provide the ECM with an
indication of engine load conditions. Engine
speed information is received from the camshaft position sensor (Hall sender in the ignition distributor) and corrected by coolant and
intake air temperatures. A heated oxygen sensor provides feedback information to the ECM
to modify the mixture as needed.
A single fuel injector (mono) is mounted in the
throttle body housing, and supplies atomized
fuel to the engine according to operating conditions specified by the ECM.
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Mono-Motronic
Ignition control is also electronic. The signals
for engine load and engine speed that are
used to control the fuel injector duration also
provide information for the basic ignition timing point. Corrections to the timing point are
made from information supplied by the
engine coolant temperature sensor, and a calculated signal is sent to the ignition coil power
output stage from the ECM.
Fuel tank ventilation is accomplished through
the use of an evaporative emissions frequency valve controlled by the ECM in the
same manner as on Motronic M2.9.
Idle speed control on the Mono-Motronic system is by two methods; either one or both
may function at the same time.
• A throttle position actuator connected to
the throttle valve moves the valve to
compensate for variations in idle speed
brought about as the result of changes in
engine loading.
• Idle speed stabilization is further
accomplished by modification of the
ignition timing point. Idle speed correction
(ISC) is a function of the ECM and is
capable of rapid response to engine speed
changes brought about by sudden load
changes. A sudden large load, such as a
radiator cooling fan switching on, will cause
a timing change and corresponding speed
change within milliseconds.
Additional functions of the ECM include:
• Operation of the fuel pump through a
ground signal sent to the fuel pump relay.
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Mono-Motronic
Inputs/Outputs
The 45-pin electronic control unit used in the
Canadian Golf CL receives input signals from
the following sources:
• Camshaft position sensor (Engine speed)
• Throttle position sensor (Engine load)
• Engine coolant temperature sensor
• Intake air temperature sensor
• Heated oxygen sensor
• Closed throttle position switch
Additional signals used as inputs are received
from the following sources:
• Air conditioner
• Automatic transmission
• Vehicle speed sensor
Outputs or actuators controlling engine operation include signals to the following:
• Fuel injector (mono)
• Ignition coil power output stage
• Throttle position actuator
Additional Systems
Fuel is sent from the fuel tank to the throttle
body by a 2-stage fuel delivery unit that is the
same as Motronic M2.9 equipped vehicles.
Fuel pressure is maintained by a mechanical
fuel pressure regulator in the throttle body
assembly. Pressure is maintained at approximately 1 bar ± 0.2 bar during engine operation by regulation of the of fuel returned to the
tank.
On Board Diagnostics
Mono-Motronic Golf CLs have On Board Diagnostic (OBD) capabilities through the use of
Scan Tools VAG 1551/1552 and VAS 5051. Idle
speed and carbon monoxide (CO) values are
regulated by the ECM and are not adjustable.
However, ignition timing can be adjusted to
baseline values as needed. Information
regarding On Board Diagnostics and engine
checks/ adjustments are available in VESIS.
Summary
• Fuel pump relay
• Early fuel evaporation relay
• Evaporative emission canister purge
regulator valve
Additional output signals are generated and
include the following:
• Malfunction indicator lamp signal
• Engine speed (rpm) signal
• Automatic transmission TCM signals
Mono-Motronic is a basic engine management system designed originally to be used
on smaller displacement engines. This was
done to take advantage of newly developed
signal processing circuits being introduced
into the automotive marketplace that would
eliminate the inefficiencies of a carburetor.
Sensor and other signal inputs, along with
actuator and other signal outputs, are shown
in the illustration on the following page.
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Mono-Motronic
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OBD II Overview
Background
OBD-II Overview
Pollution from the internal combustion
engines in cars and trucks is a concern in the
United States. California addressed these
concerns when it enacted the first air quality
standards for motor vehicles in 1961 for the
1963 model year. The California Air Resources
Board (CARB) has led the effort to reduce all
types of motor vehicle emissions nationwide.
In addition to reducing vehicle emissions,
CARB has been an innovator in related concepts such as standardized On Board Diagnostics (OBD) that help contribute to cleaner
running engines.
The United States Government is involved in
air quality standards through the Environmental Protection Agency (EPA). The EPA works
with the auto manufacturers, the Society of
Automotive Engineers (SAE), and other agencies to regulate and enforce legislation dealing with air quality.
By the early 1980s, many vehicle manufacturers were using electronics and computers to
manage fuel and ignition functions. Methods
had been developed for these systems to
diagnose problems with sensors and actuators. OBD-I refers to a requirement for vehicles sold in California, starting with the 1988
model year, to standardize these diagnostics.
The requirement stated that a partial or a
complete malfunction that caused exhaust
emissions to exceed a specified level would
illuminate a Malfunction Indicator Light (MIL).
An identification code is assigned to each malfunction.
As the graph shows, the major automotive
pollutants of hydrocarbons (HC), carbon monoxide (CO), and nitrous oxides (NO
) have
X
been dramatically reduced in California due to
the effects of CARB-sponsored legislation.
100%
80%
60%
40%
20%
0%
Emissions reductions brought about as a
result of OBD-I technology evolved into the
next generation of on board diagnostics,
OBD-II.
CO,NOx,HC
1975 1980 1985 1990 1995 2000
HC
NOx
CO
SSP 8410/143
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OBD-II Overview
OBD-II
Beginning with the 1996 model year, all
Volkswagen passenger vehicles are equipped
to meet the new OBD-II diagnostic standard.
OBD-II is a refinement of the older OBD-I
standard. These new standards encompass
more than engine operating parameters
alone. Additional engine management
components, engine and fuel systems, and
non-engine systems are monitored as part of
the OBD-II system.
OBD-II standards include:
• Standardized diagnostic connection and
location in the driver’s area
• Standardized DTCs for all manufacturers
• Retrieval of DTCs by commercially available
diagnostic equipment (generic scan tools)
• Retention of operating conditions present
during a monitored malfunction
• Standards governing when and how a
monitored malfunction must be displayed
• Standardized names for components and
systems
After establishing the set of standards as a
framework, a set of objectives was developed
to provide the basis for system operation.
The objectives include:
• Operational monitoring of all components
that have an influencing effect on exhaust
emissions
• Protection for the catalytic converter(s)
• Visual display within driver’s view
(malfunction indicator light) to signal
malfunctions in emissions-relevant
components
• On-board fault memory to store
standardized error codes
• Diagnosis capability
With the objectives firmly established, a clear
method of achieving them was designed into
the engine management system and the
ECM. The monitored components and systems include:
• Three-way catalytic converter
• Oxygen sensors
• Engine misfire detection
• Secondary air injection
• Exhaust gas recirculation
• Evaporative emissions control and system
integrity
• Fuel distribution system
• All sensors, components, and inputs
associated with the ECM
• Automatic transmission (emissions-related
functions)
84
SSP 8410/144
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OBD-II Function
OBD-II Overview
OBD-I systems verify the normal operation of
sensors and actuators by measuring voltage
drop at the component. This technique for
confirmation of operation is known as a component monitor. This method can be used to
determine short circuits to positive, short circuits to Ground, and open circuits.
OBD-II systems monitor inputs and outputs
(sensors and actuators) in the same manner
as OBD-I systems, but add comprehensive
new processes that include:
• Plausibility of signals and components of
emissions-related functions
• Monitors on functions not completely
monitored previously
• Monitors on systems not monitored
previously
Monitors, as used in this context, can take
either of two forms:
• Component monitors: the ECM looks at
the operation of individual parts of the
system.
• System monitors: the ECM operates a
component (or multiple components) to
verify system operation.
Legislation mandating OBD-II systems also
requires that the vehicle manufacturer design
the diagnostic system in a manner that permits retrieval of OBD data in a standard format using any available generic scan tool.
OBD-II data can be retrieved through one of
three data transfer protocols:
• ISO 9141 CARB
• SAE J1850 VPW
• SAE J1830 PWM
Scan tool access to the ECM on Volkswagen
vehicles is through ISO 9141 CARB. A generic
scan tool can be plugged into the Data Link
Connector (DLC), and the required communication initiated with this protocol using the
scan tool manufacturer’s instructions. The
VAG 1551/1552 and VAS 5051 can also operate as a generic scan tool using address word
33.
The OBD-II enabling legislation also allows
vehicle manufacturers to supply additional
data and functions above and beyond the
required data. This is accomplished by means
of a proprietary transfer mode which is part of
ISO 9141.
VAG 1551 Scan Tool
SSP 8410/145
VAG 1552 Scan Tool
SSP 8410/146
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OBD-II Overview
VAS 5051
The proprietary mode is accessed using
address word 01. It can provide the same data
as the generic mode, but in the more familiar
Volkswagen scan tool formats. It also provides greatly expanded data and functionality,
and is the preferred method of communication for Volkswagen technicians using the
VAG 1551/1552 and VAS 5051.
Diagnostic Trouble Codes
Diagnostic trouble codes are required by law
to be structured in a manner that is consistent
with SAE standard J2012. This standard uses
a letter to designate the system, and four
numbers to further identify and detail the malfunction. They are commonly referred to as
“P-codes” and are used in addition to the
familiar 5-digit VAG code.
VAS 5051
SSP 8410/147
Address word 33
Address word 33 gives access to the generic
scan tool function of the 1551/1552 or 5051.
This function allows for several expanded
functions.
One of the most helpful is access to “Freeze
Frame” data. This data documents exact
operating conditions under which a DTC is
stored. This can be useful in diagnosing intermittent faults.
First digit structure is as follows:
• Pxxxx for powertrain
• Bxxxx for body
• Cxxxx for chassis
• Uxxxx for future systems
Second digit structure is:
• P0xxx Government required codes
• P1xxx Manufacturer codes for additional
emissions system function; not required
but reported to the government
Third digit structure is:
• Px1xx measurement of air and fuel
• Px2xx measurement of air and fuel
• Px3xx ignition system
• Px4xx additional emission control
• Px5xx speed and idle regulation
• Px6xx computer and output signals
• Px7xx transmission
The fourth and fifth digits designate the individual components and systems.
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For example, consider a camshaft position
sensor (or related circuitry) that has a range or
performance problem. This will generate the
dual codes of P0341/16725 to be stored in
DTC memory.
Readiness Codes
OBD-II systems are required to generate a
report concerning the operational status of up
to 8 emission functions. This report is called
the readiness code, and is viewable on both
the generic scan tool and the VAG 1551/1552
and VAS 5051 scan tools.
The readiness code indicates whether a particular system or function passed the appropriate operational test and was found to be
within specification (for the duration of the
test). Malfunctions in the system that occur
later and record a DTC will not change the
readiness code. However, when the fault is
repaired and the DTC is erased, the readiness
will also be erased.
Accessing the OBD-II system with a scan tool
allows access to data that can indicate if:
• a readiness code test is running
• there is a fault
• there is no fault
If the readiness code indicates that the diagnostics have not been performed, several
methods can be used to confirm the required
operation and set the codes.
Readiness codes can be useful for several
reasons:
• During an emissions test, the readiness
code can be used to confirm system
function and may be required in some
geographical areas.
• After emissions system repairs, proper
operation can be confirmed by using the
readiness code.
OBD-II Overview
Readiness code values
Digit position
12345678
0 Three Way Catalyst
0 Catalyst Heating (always 0)
0 Evaporative Emissions System
0 Secondary Air Injection System
0 Air Conditioning
0 Oxygen Sensor
0 Oxygen Sensor Heater
0 Exhaust Gas Recirculation - EGR
Diagnostic Function
(Fuel tank vent system)
(always 0)
(no current diagnostic function-always 0)
(always 0)
SSP 8410/29
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OBD-II Overview
Setting readiness codes
Several methods exist for setting readiness
codes. Some methods will not work with
some systems, so the appropriate VESIS
repair information must be consulted for the
correct procedure.
The first method of setting the readiness
code is by driving the vehicle in a prescribed
manner called the Federal Test Procedure 72
(FTP72) driving cycle. This procedure, as
shown in the accompanying illustration,
requires that the vehicle be driven 7.5 miles
(12.07 KM) over a period of 1372 seconds (22
minutes, 52 seconds) at a maximum speed of
56.67 m.p.h. (91.2 kph) from a cold start. This
procedure allows all of the diagnostic procedures to run and if completed successfully,
the readiness code will set. Carrying out this
procedure can be difficult due to the time factor involved and the need for a cold start.
The second method for setting readiness
codes involves the use of scan tools VAG
1551/1552 or VAS 5051. In this instance, a
road test, or “short trip,” is used with the
scan tool overriding some of the normal ECM
programming to force diagnostics to run. This
procedure is run following VESIS procedures
specific for each vehicle and system. It considerably shortens the time required to set
the readiness code.
The newest method of setting readiness
codes allows the technician to use the appropriate scan tool, and set the code without the
need to drive the vehicle. This procedure can
only be used on the newer engine management systems where it has been programmed into the ECM. Specific VESIS
procedures must be followed for each individual version.
v [km/h]
100
80
60
40
20
0
200
400
600
800
1000
1200
SSP 8410/148
1372
t [s]
Summary
OBD-II systems are basically enhanced and
expanded versions of OBD-I systems. Additional parts of the engine as well as other
related systems and functions are included in
the diagnostic structure. In practice, most of
the changes are software changes to the
ECM rather than major hardware changes.
The new components simply provide more
data to take advantage of the new computing
power resulting in a dramatic reduction in
total vehicle emissions.
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Motronic M5.9 Overview
System Description
Motronic M5.9 Overview
Motronic Engine Management Systems
moved to the next level of development with
model year 1996. This significant date marked
the required compliance with On Board Diagnosis II (OBD-II) standards as mandated by
the California Air Resources Board (CARB)
and the United States government.
All Motronic M5.9 engine management systems comply with OBD-II standards. These
standards apply to all passenger vehicles sold
in the United States with different compliance
levels being phased in over a period of several
years.
The Motronic M5.9 system also adds component and system monitors to the diagnostic
capabilities.
Component monitors allow the Motronic
ECM to check for plausible signals by cross
checking against another component.
Example:
The Motronic ECM compares the Engine
Coolant Temperature (ECT) sensor signal
against a map based on the Intake Air Temperature (IAT) sensor signal at the time the
engine was started.
If after a specified time the ECT signal is more
than 20° C from the mapped point, the ECM
believes this to be implausible for the running
condition, and sets an appropriate DTC.
SSP 8410/123
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Motronic M5.9 Overview
Motronic M5.9 systems operate with the
same functionality as their predecessors, but
add the second generation of diagnostic capabilities. The diagnostic system is integrated
into the engine management system, and
continuously monitors its own emissionsrelated components, as well as other vehicle
systems that affect emissions. Furthermore,
operation of some existing components has
been modified and several new components
have been added.
Enhancements over previous Motronic systems can include:
• Monitoring of three-way catalytic converter
function
• Diagnosis of heated oxygen sensor
response, voltage, and aging
• Diagnosis of oxygen sensor heating
• Diagnosis of fuel tank and venting system
integrity
• Diagnosis of evaporative emissions flow
• Engine misfire detection
• Enhanced diagnostics for input and output
components by checking function and
signal plausibility in addition to open and
short circuits
• Expanded and standardized DTC
capabilities
• Status of emissions-related diagnostic
routines (readiness code)
Input/Outputs - Motronic M5.9
A 68-pin ECM receives inputs from sensors
which are essentially the same as on
Motronic M2.9 systems. These include the
following sources:
• Engine Speed (RPM) sensor G28
• Intake Air Temperature (IAT) sensor G72
• HO2S, B1S1 G39 (pre-catalyst)
• Engine Coolant Temperature (ECT) sensor
G62
• Camshaft Position (CMP) sensor G40
• Mass Air Flow (MAF) sensor G70
• Knock Sensors (KS) G61 and G66
• EGR temperature sensor G98
• Signals received from the Speedometer
Vehicle Speed Sensor (VSS) G22, A/C
system, Transmission Control Module
(TCM) J217, and electrical system voltage
Throttle position information formerly
received from the throttle valve potentiometer
G69 has been expanded and combined into
the following new component:
• Throttle valve control module J338 with
Throttle Position (TP) sensors G69 and G88,
and Closed Throttle Position (CTP) switch
F60
New sensors or signals added to the input
side of the system include:
• HO2S, (G108) (post-catalyst)
90
• Leak Detection Pump (LDP) reed switch
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Motronic M5.9 Overview
The outputs or actuators are essentially the
same as on Motronic M2.9, and include the
following:
• Evaporative Emission (EVAP) canister purge
regulator valve N80
• Fuel injectors (N30 - N33, N83, N84)
• Ignition coil N152 with power output stage
N157
• Fuel Pump (FP) relay J17 and Fuel Pump G
• EGR vacuum regulator solenoid valve N18
• Secondary Air Injection (AIR) pump relay
J299 and Secondary Air Injection (AIR)
pump V101
• Secondary Air Injection (AIR) solenoid valve
N112
• Oxygen sensor heater relay J278
• Signals sent to the TCM J217, Instrument
cluster
The IAC valve (idle stabilizer) has been eliminated and its function replaced by:
• Throttle valve positioner V60, which is part
of the throttle valve control module J338.
New components or signals added to the out-
put side of the system include:
• Evaporative Emission (EVAP) canister purge
solenoid valve N115
Adaptation of system variables occurs in
Motronic M5.9 systems just as in earlier versions, and there are no mechanical engine
settings or adjustments to be made. However, if the battery is disconnected, or if
power is interrupted to the ECM, the learned
or adapted values may be erased. DTCs and
readiness codes may also be erased. The
adapted value for the throttle valve control
module J338 must be reset to avoid driveability problems.
Additional Systems
Fuel delivery from the tank is the same as the
Motronic M2.9 versions, with pressure maintained by the manifold vacuum-operated fuel
pressure regulator on the fuel injector rail
assembly.
Sensor inputs, other input signals, actuator
signals and other output signals are shown in
the illustration on the following pages. The
illustration represents components that are
installed on several different engine types.
Certain engines will not have some of the
listed components.
• Fuel cut-off valve shut-off relay J335
• LDP vacuum solenoid switch
91
Page 96
Motronic M5.9 Overview
VR-6 system overview
Heated Oxygen Sensor (HO2S) (G39)
(Pre-CAT sensor)
Heated Oxygen Sensor (HO2S) 2 (G108)
(Post-CAT sensor)
Mass Air Flow (MAF) Sensor (G70)
EGR Temperature Sensor (G98)
Knock Sensor (KS) 1 (G61)
Knock Sensor (KS) 2 (G66)
Engine Speed (RPM) Sensor (G28)
Camshaft Position (CMP) Sensor (G40)
integrated in distributor
on the 2.0L
Speedometer Vehicle Speed
Sensor (VSS) (G22)
Intake Air Temperature (IAT)
Sensor (G72)
Engine Coolant Temperature
(ECT) Sensor (G62)
Throttle Valve Control Module (J338)
integrating:
Throttle Position (TP) Sensor (G69)
Throttle Position (TP) Sensor (G88)
Closed Throttle Position (CPT)
Switch (F60)
92
Additional signals
Page 97
Motronic M5.9 Overview
Secondary Air Injection (AIR)
Pump Motor (V101)
Secondary Air Injection (AIR)
Solenoid Valve (N112)
EGR Vacuum Regulator Solenoid
Valve (N18)
Evaporative Emission (EVAP) Canister
Purge Regulator Valve (N80)
Leak Detection Pump (LDP) (V144)
Evaporative Emission (EVAP) Canister
Purge Solenoid Valve (N115)
Throttle Valve Control Module (J338)
integrating:
Throttle Position (TP) Actuator (V60)
Distributor-less Ignition
integrating:
3 independent ignition coils
(for 6-cylinder engine)
Fuel Injectors (N30), (N31), (N32), (N33)
(4-cylinder)
+ (N83), (N84)
(6-cylinder)
Malfunction Indicator Lamp (MIL)
Additional signals
93
Page 98
Motronic M5.9.2 Overview
Inputs/Outputs - Motronic M5.9.2
Motronic M5.9.2 is a slightly modified version
of the earlier M5.9 system, with a new 80-pin
ECM. The ECM accommodates new functions, input sensors and actuators. Enhancements improve starting and fuel economy,
and reduce exhaust emissions.
On some models, cruise control is no longer a
separate system; its functions are now integrated into the ECM on vehicles so equipped.
On these vehicles, the cruise control inputs to
the ECM can be monitored in measuring
block values using the scan tool. The ECM is
also now linked to the CAN-bus for communication with other systems (see SSP # 186,
The CAN Data Bus).
Most of the input sensors used with this new
system are the same as on the earlier versions. However, several sensors have been
modified to enhance their performance or to
adapt them to engine design changes.
Changed or modified components on the
input side of the system include:
• Mass Air flow (MAF) sensor G70
• Camshaft Position (CMP) sensor G40
Changes to the output side of Motronic
M5.9.2 system include:
• Air-shrouded injectors
• Distributor-less ignition on 4-cylinder
engines with either:
Separate power output stages and ignition coils for each cylinder
Or, two double-ended ignition coils and
two power output stages
• Wastegate bypass regulator valve N75
Sensor inputs, other input signals, actuator
signals and other output signals are shown in
the illustration on the following page.
• Planar oxygen sensors
• Barometric Pressure (BARO) sensor F96
(1.8T)
• Cruise control inputs (vehicles with cruise
control)
New input signals include:
• Brake pedal position switch F47, (vehicles
with cruise control)
• Clutch vacuum vent valve switch F36
(vehicles with cruise control)
• Cruise control switches E45 and E227,
(vehicles with cruise control)
• Brake light switch F
94
Page 99
1.8 liter turbo, system overview
Heated Oxygen
Sensor (H02S)
G39
Oxygen Sensor
behind TWG
G130
Mass Air Flow
Sensor G70
Intake Air
Temperature
Sensor G72
Knock Sensors
G61 & G66
Engine Control
Module (ECM) J220
Motronic M5.9.2 Overview
Fuel Pump (FP) G6
with Fuel Pump
Relay J17
Fuel Injectors
N30, N31, N32, N33
Power Output Stage
N122
Ignition Coils
N, N128, N158, N163
Camshaft Position
(CMP) Sensor
G40
Engine Speed
(RPM) Sensor
G28
Engine Coolant
Temperature
(ECT) Sensor G62
Barometric
Pressure (BARO)
Sensor F96
Throttle Valve
Control Module
J338
• Throttle Position
(TP) Sensor G69
• Closed Throttle Position
(CTP) Switch F60
• Throttle Position
(TP) Sensor G88
Additional
signals
Data Link Connector
(DLC)
Throttle Valve Control
Module J338
• Throttle Position
Actautor V60
Evaporative Emission
Canister Purge
Regulator Valve N80
Wastegate Bypass
Regulator Valve
N75
Additional
signals
SSP 8410/116
95
Page 100
Notes
96
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