OTHER Self Study Program 941003 – Engine Management Systems SSP-941003-Audi-engine-management-systems
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Engine
Management
Systems
Self-Study Program
Course Number 941003
Design and Function
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Audi of America, Inc.
Service Training
Printed in U.S.A.
Printed 5/2000
Course Number 941003
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 Audi
Worldwide Repair Information System for
information that may supersede any
information included in this booklet.
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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
Continuous Injection System ................................................................27
CIS ............................................................................................................28
K-Jetronic with Lambda control ................................................................30
CIS-E .........................................................................................................32
CIS-E III .....................................................................................................35
CIS Turbo ..................................................................................................38
CIS-E Motronic .........................................................................................39
Motronic M2.3.2 Overview ....................................................................43
System description ...................................................................................43
Inputs/Outputs - 20 Valve Turbo Motronic M2.3.2 ..................................47
Inputs/Outputs - 4.2 Liter V8 Motronic M2.3.2 .......................................51
On Board Diagnostics ...............................................................................54
Motronic M2.3.2 Component Summary ...............................................55
Input sensors ............................................................................................57
Actuators (outputs) ..................................................................................72
Review ......................................................................................................83
MPI - Multi Port Fuel Injection system .................................................85
System description ...................................................................................85
MMS 100/200 overview ...........................................................................86
On Board Diagnostic (OBD) ......................................................................86
MMS 100/200 System Components ........................................................87
MMS 300/311 overview, system description and comparison ..............104
OBD-II Overview ..................................................................................107
Background .............................................................................................107
OBD-II .....................................................................................................108
Diagnostic Trouble Codes ......................................................................110
Readiness Codes ....................................................................................111
Summary ................................................................................................112
Table of Contents
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Table of Contents
MMS 400/410/411 Overview ...............................................................113
Oxygen Sensor(s) (O2S) behind
Three Way Catalyst (TWC) G130/G131.................................................. 114
Sensor for EVAP canister G172 ..............................................................115
Data Link Connector (DLC) .....................................................................115
Secondary Air Injection (AIR) ..................................................................116
Leak Detection Pump (LDP) V144 ..........................................................117
Motronic M5.4.2 Overview ..................................................................119
System Description ................................................................................119
Input/Outputs - Motronic M5.4.2 ..........................................................120
Additional Systems .................................................................................121
A8 Motronic M5.4.2 system overview ..................................................122
Motronic M5.4.2 Components ...............................................................125
Input Sensors .........................................................................................126
Actuators (outputs) .................................................................................131
Motronic M5.9.2 Overview .................................................................. 139
System Description ................................................................................139
Input/Outputs - Motronic M5.9.2 ..........................................................140
Additional Systems .................................................................................141
1.8 liter turbo, system overview ............................................................142
Motronic M5.9.2 Component Differences ..........................................143
Engine Control Module J220 ..................................................................143
Combined Sensors/Actuators .................................................................144
Input Sensors .........................................................................................147
Actuators (outputs) .................................................................................152
Review ...................................................................................................156
Motronic ME 7 ......................................................................................159
Pathways ................................................................................................159
Components of Motronic ME 7.............................................................. 159
Electronic throttle control .......................................................................164
Review ...................................................................................................169
Level one course preparation ..............................................................171
Critical Thinking Skills .............................................................................171
Audi Electronic Service Information Service (AESIS) navigation ............172
Audi HELP line/Tech-tip line ...................................................................172
Diagnostic and Special Tools ..................................................................173
Review questions ...................................................................................173
Suggested reading and reference .......................................................173
Glossary ................................................................................................175
Post-test ................................................................................................179
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Introduction
Introduction
The origins of Audi engine development can
be traced back to a 1913 4-cylinder liquidcooled engine designed by August Horch
(1868-1951) in Zwickau, Germany. This greatgrandfather of the modern Audi 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 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 system.
Course goals
review principles of engine operation
explain the progression of engine
management systems used by Audi
provide an in-depth understanding of both
previous engine management systems and
the state-of-the-art engine management
systems in use today
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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 for a specified
number of pulses using the starter, while
applying Wide Open Throttle (WOT).
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 to 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 owners manual.
Octane is a relative measure showing the
gasolines 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.
The CLC number is derived from both the
RON and the MON as follows:
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 with higher octane numbers resist
temperature and pressure better, and therefore have less tendency to self-ignite.
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).
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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 Audi Owners Manuals list recommended
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 volume. This is referred to as the
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).
stoichiometric
Definition:
rich
A
relation to the stoichiometric ratio.
A
relation to the stoichiometric ratio.
mixture contains more fuel than air in
lean
mixture contains more air than fuel in
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
1.30.
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
loop operation
after either a cold or warm start. Conversely,
engine operation with a valid oxygen sensor
signal is called
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.
. This condition can occur
closed loop operation.
open
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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 technology created a new perspective in how fuel and ignition system management is viewed. Starting with the Fox and the
100LS in 1975, Audi began replacing carburetors with fuel injection. The Bosch KJetronic fuel injection system that was
used seems very basic by todays standards,
but it represented a giant technological leap
forward at the time. Fuel delivery was by individual fuel injectors in a continuous flow with
the fuel pump relay containing the only electronics in the system. The ignition continued
to be handled by a breaker point distributor.
Advances in computer technology, combined
with new circuit designs, allowed electronic
control of the fuel and the ignition in later version of these systems.
Mixture control feedback through the use of
oxygen sensors allows more precise metering of the fuel. Ignition system feedback
through the use of knock sensors allows optimum spark timing. These feedback loops
allowed engine operation to be continuously
corrected to compensate for changing operating conditions.
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 systems 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
following:
Battery
Coil
Trigger (either breaker points or electronic)
Electronic signal amplification and advance
control
primary
, and include the
Components using high voltage are classified
secondary
as
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 electronically), the magnetic
field around the primary windings collapses
and induces a higher voltage in the secondary
windings.
, and include the following:
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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
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).
dwell
. Dwell is the length of
Principles of engine operation
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Principles of engine operation
breaker point style ignition system
In a
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 (½ 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
state ignition system
replacing the ignition points with a Hall
sender, more consistent and reliable ignition
system performance was attained.
was developed. By
, the
solid
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Hall sender
The
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 Halleffect transistor, current flow stops.
is a solid-state, semi-conduc-
Principles of engine operation
Operating voltage is supplied by either an ignition 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.
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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 the 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. The electrode
must get hot enough to burn off any carbon
accumulation by the time the engine reaches
operating temperature, but not hot enough to
burn the insulator (or electrode). Classifications exist for hot, cold or anywhere in
between.
cold
A
heat from the combustion process rapidly
through the threads to the head and cooling
system.
spark plug is a one that transfers the
hot
A
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 AESIS).
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.
spark plug is a one that transfers the
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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.
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 has 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 941903, 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.
For maximum efficiency, the internal surface
area exposed to the exhaust flow must be as
large as possible. For that reason, the noble
metals 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 washcoat is applied. Other types of converters
are used by other automotive manufacturers,
but all Audis 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.
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Catalytic Converter Operation
Principles of engine operation
The three-way catalytic converter takes the
major exhaust pollutants of:
NOx (nitrous oxides- several)
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 NOx component.
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.
The output from a normally operating threeway catalytic converter consists primarily of:
N2 (nitrogen)
CO2(carbon dioxide)
H2O (water)
The reduction process is most efficient in a low
O2 environment, and the oxidation process is
most efficient in a high O2 environment.
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 on previous page). Oxygen sensor
functionality varies by engine management
system. Please refer to the appropriate chapter for system specific oxygen sensor information.
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 effects 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
Audi 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
sensors 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 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 the component, 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 the component,
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
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.
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+
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
operating 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?
NOT
an
4. Which of the following components is
a component of gasolines ability
NOT
to pre-ignite?
a. Research octane number
b. Motor octane number
c. Cetane
d. Anti-knock index
5. Which of the following is
ponent 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
NOT
a com-
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-prod-
ucts is
sphere?
a. Hydrocarbons (HC)
b. Oxygen (O2)
c. Carbon monoxide (CO)
d. Oxides of Nitrogen (NO
harmful to the atmo-
NOT
)
x
25
Page 30
Notes
26
Page 31
Continuous Injection Systems (CIS)
Continuous Injection System
In 1975, Audi introduced Bosch K-Jetronic
fuel injection on the 100 LS model. This class
of fuel injection system is characterized by
the continuous flow of fuel from the fuel
injectors and is more commonly known as
CIS (Continuous Injection System).
Audi used several versions of this hydromechanical fuel system due to its efficient
and consistent engine operation.
CIS:
Completely hydro-mechanical with the
fuel pump relay being the only electronic
component.
CIS-Lambda:
but with an oxygen sensor providing
feedback to an electronic control unit which
continuously adjusts mixture.
Similar in operation to CIS,
CIS-E:
providing engine operating data to an
electronic control unit, and an oxygen
sensor providing mixture feedback
information. Idle speed is controlled
electronically by a variable throttle bypass
valve called an idle air control valve, or idle
stabilizer.
CIS-E III:
similar to CIS-E, but with electronic ignition
and integrated knock regulation. Also
features electronic fault recognition and
memory.
CIS Turbo:
combining the CIS lambda fuel system with
electronic ignition and boost control. Later
versions added knock sensors to the
ignition system.
CIS-E Motronic:
system, similar to CIS-E III, but with
adaptive mixture control.
Electronic system with sensors
An engine management system
An engine management system
An engine management
27
Page 32
Continuous Injection Systems (CIS)
CIS
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 continuously
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.
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. Resistance
is greater, resulting in a leaner fuel mixture.
28
Page 33
Continuous Injection Systems (CIS)
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 V also supplied by
starter 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
approximately 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.
Since there are essentially no electronic controls to this system, there are no sensors or
actuators.
Additional systems
Fuel is supplied to the CIS system by an
externally mounted fuel pump with an accumulator and filter on the outlet side. Pressure
is maintained by a fuel pressure regulating
relief valve integral with the fuel distributor.
29
Page 34
Continuous Injection Systems (CIS)
K-Jetronic with Lambda control
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 instantaneous running
conditions. This provided more consistent
running characteristics, as well as minimizing
the amount of adjustment necessary 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 fuel return line. When lower chamber
pressure drops, the diaphragm flexes downward, opening a larger fuel orifice.
30
Page 35
Continuous Injection Systems (CIS)
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.
CIS with Lambda control was also available
with a turbocharger on early 5000 models.
The turbocharger added additional air to the
engine which improved performance by making use of heat that would be otherwise
wasted. A mechanical wastegate limited
boost pressure, but fuel control remained
essentially the same.
This system was the beginning of todays
adaptive engine management systems.
Inputs/Sensors
The addition of an Oxygen sensor control unit
required a minimum number of input signals
including:
Oxygen sensor thermo-switch (to switch
off oxygen sensor control on a cold engine)
Oxygen sensor
Full throttle enrichment switch
Outputs/Actuators
Only one output signal is generated:
Oxygen sensor frequency valve
31
Page 36
Continuous Injection Systems (CIS)
CIS-E
Beginning in 1984, Audi expanded the capabilities of the CIS fuel injection system. New
features include:
Control pressure regulator and frequency
valve replaced by an Differential Pressure
Regulator (DPR).
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).
Fuel system pressure now regulated by an
external fuel pressure regulator.
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Continuous Injection Systems (CIS)
The major difference between CIS-Lambda
and CIS-E is the replacement of the control
pressure regulator and frequency valve with
an electro-hydraulic actuator. This actuator is
more commonly called a Differential Pressure
Regulator (DPR).
The differential pressure regulator receives a
varying current signal from the CIS-E control
unit. This energizes an electro-magnet, which
deflects a valve plate to create a difference in
the pressures between the upper and the
lower chambers of the fuel distributor. As current is increased, the plate valves deflects
more which restricts fuel flow to the upper
chamber of the fuel distributor.
The reduction in fuel pressure in the lower
chamber causes the pressure regulating
valves at the fuel injector outlets to open further, increasing the quantity of fuel delivered
to the injectors. This increases fuel pressure
to the injectors and allows greater fuel flow
for a given amount of sensor plate travel.
The operating range of the differential pressure regulator during oxygen sensor control is
between 0 mA and +20 mA, allowing for
more accurate control of the fuel trim, as well
as decreased maintenance.
Continuous, variable control of idle speed is
built into the CIS-E fuel injection system. This
is accomplished by regulating the flow of air
around the throttle valve by an electronically
controlled bypass valve called an idle air control valve or idle stabilizer.
Compensation is made for differing engine
load conditions such as those encountered
with a cold engine or when the air conditioning is switched on. The idle air control valve
replaces the function of the auxiliary air regulator.
33
Page 38
Continuous Injection Systems (CIS)
Inputs/Sensors
CIS-E fuel injection control units require several sensor inputs to calculate the current
value required by the differential pressure
regulator. These signals include:
Engine coolant temperature sensor
Airflow sensor potentiometer
Oxygen sensor
Engine RPM signal from ignition control
unit
Idle switch
Full throttle enrichment switch
Outputs/Actuators
Output signals generated are:
Differential pressure regulator
Idle stabilizer
34
Page 39
Continuous Injection Systems (CIS)
CIS-E III
Model year 1987 brought the next changes in
CIS-based fuel injection systems.
CIS-E III added a separate knock sensor control unit with On Board Diagnosis through blink
codes displayed in the instrument cluster.
The operating range of the differential pressure regulator during oxygen sensor control
has been modified. The new range is
between -10 mA and +10 mA with an adjusting point of 0 mA. This allows better engine
operation in the event of an electrical failure
and minimal ECM correction to a properly
adjusted engine.
The addition of knock control allows the
engine to operate at a higher level of efficiency. This is accomplished by optimizing the
combustion process according to fuel grade.
Inputs/Sensors
CIS-E III fuel injection and ignition control
units require several sensor inputs to calculate the values required for engine operation.
These inputs include signals from:
Engine coolant temperature sensor
Airflow sensor potentiometer
Oxygen sensor
Hall sender in the ignition distributor
Knock sensor
Altitude sensor
Idle and full throttle switches
35
Page 40
Continuous Injection Systems (CIS)
Outputs/Actuators
Output signals generated to operate the
engine include:
Differential pressure regulator signal
Idle stabilizer signal
Carbon canister shut-off valve signal
Cold start valve signal
Ignition signal to the power output stage
Malfunction indicator light
On Board Fault Memory
CIS-E III engine management systems have
the ability to store information concerning certain component malfunctions in memory.
Faults are stored in either the ignition control
module or the fuel injection control module.
Any malfunctions recorded will be erased
when the ignition is switched off.
The system can recognize approximately 17
different 4-digit fault codes, and the fault
memory can be accessed using scan tool
VAG 1551. Model year 1988 vehicles require
the use of adaptor VAG 1550/2 with system
access through a connection to the fuel pump
relay. Later vehicles access this data through
the data link connector (DLC).
Sensor inputs, actuator signals and other output signals are shown in the illustration on the
following page.
36
Page 41
Continuous Injection Systems (CIS)
37
Page 42
Continuous Injection Systems (CIS)
CIS Turbo
1983 was a landmark year for Audi with the
introduction of its first engine management
system. CIS Turbo integrated both fuel injection and ignition timing into one control unit.
The early fuel/timing control unit, commonly
referred to as the MAC-02, used inputs from
the following sensors for engine control:
Intake air temperature
Engine coolant temperature
Boost pressure transducer (integral with
the fuel/timing control unit)
Engine speed sensor
Crankshaft position (reference) sensor
Camshaft position (Hall sender in
distributor)
Oxygen sensor
Idle/full throttle switches
The signals generated to operate the engine
included outputs to the following:
Ignition control unit
Frequency valve
Fuel pump relay
Ignition timing was controlled by a calculation
map derived from engine RPM, boost pressure, and intake air temperature.
In 1986, several modifications were made
with the addition of a new control unit known
as the MAC-07. A new single knock sensor
allowed optimized ignition timing, and minimized the possibility of engine knock under
boost.
A wastegate frequency valve was also
included giving more accurate control over
total boost pressure. This component functioned at the command of the ECM by supplying boost pressure to the upper chamber of
the wastegate. The pressure acting on the
wastegate diaphragm controlled wastegate
operation.
The final change to CIS Turbo was mid year
1989. The newest control unit, MAC-11,
added a second knock sensor for even more
accurate control of ignition timing.
On board diagnostics for this system were
limited. Several fault indicators can be read
through tachometer needle position on the
instrument cluster on some models only.
38
Page 43
Continuous Injection Systems (CIS)
CIS-E Motronic
With the introduction of the 4-cylinder Audi 80
and 90 models in the North American market,
CIS fuel injection systems evolved into CIS-E
Motronic engine management.
This system and its individual components
are very similar to CIS-E III in operation, but
combine fuel injection control and ignition
control into a single electronic Engine Control
Module (ECM).
Located behind the air conditioner evaporator
assembly, the 35-pin CIS-E Motronic ECM
features encompass:
Fuel injection control
Ignition control by ECM map
Individual cylinder selective knock
regulation
Oxygen sensor regulation with adaptive
learning
Idle speed control
Fuel tank ventilation control
Permanent fault memory via blink code
The operating range of the differential pressure regulator during oxygen sensor control
has been expanded due to the adaptive learning capability (see Glossary). The rich adaptive
limit is +23 mA, and the lean limit is -16 mA.
This new capability allows the engine management system to compensate for changes
in the engines operating conditions such as
altitude changes, intake air leaks, or other
deviations from normal running.
The adaptive learning capability necessitates
new procedures when engine settings need
to be adjusted, since engine idle speed is preprogrammed into the ECM and cannot be
adjusted.
39
Page 44
Continuous Injection Systems (CIS)
Inputs/Sensors
CIS-E Motronic engine management receives
operating inputs from the following sensors:
Ignition distributor with Hall sender (engine
RPM)
Air sensor potentiometer (engine load)
Idle and full throttle switches (throttle
position)
Coolant temperature
Heated oxygen sensor
Knock sensor
Additional input is received from the air conditioning system.
Actuators/Outputs
CIS-E Motronic engine management systems
generate operating outputs to operate the following actuators:
Differential pressure regulator
Ignition coil power output stage
Cold start valve
Idle stabilizer
Carbon canister frequency valve
Carbon canister shut-off valve
An signal is also sent to the instrument cluster
for tachometer, dynamic oil pressure, malfunction indicator light, and the Auto-Chek system.
40
Page 45
Continuous Injection Systems (CIS)
On Board Fault Memory
Permanent fault memory as applied to CIS-E
Motronic means that any malfunctions
recorded will be retained when the ignition is
switched off. Checking and clearing the fault
memory is generally done during maintenance, or if the malfunction indicator in the
instrument cluster is illuminated.
The system can recognize up to 15 different
4-digit fault codes. The fault memory can be
accessed using scan tool VAG 1551. Model
year 1988 vehicles require the use of adaptor
VAG 1550/2 with system access through a
connection to the fuel pump relay. Later vehicles access this data through the data link
connected (DLC).
Sensor inputs, actuator signals and other output signals of the 1988 - 1992 Audi 80, 2.0
liter, engine code 3A are shown in the illustration on the following page.
41
Page 46
Continuous Injection Systems (CIS)
42
Page 47
Motronic M2.3.2 Overview
System description
Motronic M2.3.2 Overview
Audi first introduced Motronic Engine Management on the 1990 V8 Quattro with the allaluminum 3.6 liter engine. For the 1993
model year, both the 20 Valve 5-cylinder 2.22
liter engine and the 4.2 liter V8 engine were
equipped with Motronic M2.3.2.
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 engines momentary operating conditions.
This information is used as the basis for the
ECMs 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.
43
Page 48
Motronic M2.3.2 Overview
Functional overview
Motronic M2.3.2 uses engine speed and load
as its primary inputs. An inductive sensor
mounted on the cylinder block measures crankshaft speed at the flywheel, and provides the
engine speed signal. A second induction sensor (mounted near the first) signals crankshaft
position which provides a reference point.
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.
Engine load information is received from the
Mass Air Flow (MAF) sensor G70, which has
no moving parts.
All Audi engine management systems with
oxygen sensor(s) 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 opening time
or duration needs to be lengthened or shortened to achieve the optimum air/fuel ratio of
14.7: 1. This is referred to as
Glossary).
Motronic M2.3.2 engine management takes
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
adaptation
(see Glossary).
(see
44
Page 49
Motronic M2.3.2 Overview
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).
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 signals the ECM to:
disable the A/C compressor
disable the EVAP system
stabilize ignition timing and idle speed
stabilize idle speed
Idle Air Control (IAC)
Idle air volume via Map control
Start control
Correction for A/C switched on
Correction for transmission in gear
Exhaust Gas Recirculation (EGR)
EGR via map control
On Board Diagnostic (California only)
Fuel Tank Ventilation
Fuel tank ventilation via map control
Advantages of adaptive learning include:
optimal fuel economy and driveability
reduced emissions
reduced maintenance
Improved driveability
Note:
When diagnosing oxygen sensor adaptation
faults, be sure to inspect the following:
Motronic engine management systems consist of, and perform the following functions:
Sequential Fuel Injection
Fuel injection via map control
Starting enrichment
Controlled ignition system
After start enrichment
Acceleration enrichment
Fuel deceleration shut-off
Maximum engine speed limitation
Oxygen sensor control
Vehicle speed limitation (130 m.p.h.)
Ignition timing via map control
Dwell angle control
Temperature correction
Starting control
Digital idle stabilization
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 areas, if not well sealed, can
lead to an inaccurate air/fuel mixture, resulting in poor driveability and possible adaptation
faults.
Always check the basics first!
Selective cylinder knock control
45
Page 50
Motronic M2.3.2 Overview
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.
The last illustration shows the system adapting to a rich running condition. This could be
the result of excessive fuel pressure or faulty
injectors, for example.
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
46
Part throttle adaptation is also referred to as:
Multiplicative
For definitions, refer to the Glossary.
Page 51
Inputs/Outputs - 20 Valve Turbo Motronic
M2.3.2
Motronic M2.3.2 Overview
The 55-pin ECM used on 20-valve turbo
M2.3.2 equipped vehicles receives signals
from several input sources. These include the
following:
Engine Speed (RPM) sensor G28
Crankshaft Position (CKP) sensor G4
Camshaft Position (CMP) sensor G40
Mass Air Flow (MAF) sensor G70
Engine Coolant Temperature (ECT) sensor
G62
Intake Air Temperature (IAT) sensor G42
Heated Oxygen Sensor (HO2S) G39
Throttle Position (TP) sensor G69
Closed Throttle Position (CTP) switch F60
Knock Sensor(s) (KS) G61/G66
Barometric Pressure (BARO) Sensor F96
Manifold Absolute Pressure (MAP) Sensor
G71 (component of Motronic ECM)
ECM output to actuators controlling engine
operation include:
Fuel injectors N30-N33, N83
Idle Air Control (IAC) valve N71
Ignition Coil Power Output Stages N122,
N192
Fuel Pump (FP) relay J17
Evaporative Emissions (EVAP) Canister
Purge Regulator Valve N80
Wastegate Bypass Regulator Valve N75
Several other systems require input from the
Motronic M2.3.2 system, or provide input to
alter the engine management.
Sensor inputs, other input signals, actuator
signals and other output signals on the 20
valve 2.22 liter turbo engine are shown in the
illustration on the following pages.
Additional signals used as inputs include:
Air conditioner (compressor and/or system
on)
Battery voltage
Speedometer Vehicle Speed Sensor (VSS)
Electronic Engine Coolant Temperature
(ECT) Thermal Switch F76
47
Page 52
Motronic M2.3.2 Overview
20 V 2.22 liter Turbo
48
Page 53
Motronic M2.3.2 Overview
49
Page 54
Motronic M2.3.2 Overview
Notes:
50
Page 55
Inputs/Outputs - 4.2 Liter V8 Motronic
M2.3.2
Motronic M2.3.2 Overview
The 55-pin ECM used on 4.2 Liter V8 M2.3.2
equipped vehicles receives signals from several input sources. These include the following:
Engine Speed (RPM) sensor G28
Crankshaft Position (CKP) sensor G4
Camshaft Position (CMP) sensor G40
Mass Air Flow (MAF) sensor G70
Engine Coolant Temperature (ECT) sensor
G62
Intake Air Temperature (IAT) sensor G42
Heated Oxygen Sensor (HO2S) G39
Throttle Position (TP) sensor G69
Closed Throttle Position (CTP) switch F60
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)
Transmission Control Module (TCM) J217
ECM output to actuators controlling engine
operation include:
Fuel injectors N30-N33, N83-N86
Idle Air Control (IAC) valve N71
Ignition Coil 1 with Power Output Stage
N70
Ignition Coil 2 with Power Output Stage
N127
Fuel Pump (FP) relay J17
Evaporative Emissions (EVAP) Canister
Purge Regulator Valve N80
Heated Oxygen sensor (HO2S) control
module J208
EGR vacuum regulator solenoid valve N18
Several other systems require input from the
Motronic M2.3.2 system, or provide input to
alter the engine management.
Sensor inputs, other input signals, actuator
signals and other output signals on the 4.2
liter V8 are shown in the illustration on the following pages.
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Motronic M2.3.2 Overview
4.2 liter V8
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Motronic M2.3.2 Overview
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Motronic M2.3.2 Overview
On Board Diagnostics
Motronic M2.3.2 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
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Motronic M2.3.2 Component Summary
Motronic M2.3.2 Component
Summary
Fuel system components
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 M2.3.2 Component Summary
Engine Control Module (ECM) J220
The 55-pin ECM must be supplied with the
appropriate power sources and Grounds to
function properly. Additionally, the ECM is
coded with a vehicle speed limiter function.
If a new ECM is installed, the ECM must be
coded. This is accomplished using a jumper
harness connector which completes a Ground
circuit in the ECM.
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.
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Motronic M2.3.2 Component Summary
Input sensors
Motronic engine management systems rely on 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
hot-wire mass air flow sensor
The
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.
is
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.
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.
Operation:
Air flows past the hot wire 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.
Note:
Wait20 seconds after engine shutdown
before removing connector from G70.
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Throttle Position (TP) sensor G69, Closed
Throttle Position (CTP) Switch F60
The throttle position sensor G69 is a potentiometer connected to the throttle valve shaft.
The signal generated is used by the ECM to
determine driver input.
The closed throttle position switch F60 is integral with G69, and is used to determine throttle position and boost regulation
(turbocharged engines).
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. F60 operates by completing a Ground circuit to the Motronic
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 M2.3.2 Component Summary
Crankshaft Position (CKP) sensor G4
The Crankshaft Position (CKP) sensor is an
inductive pickup
is located on the left side of the engine in the
transmission bellhousing. The sensor is used
to identify TDC number one cylinder.
A pin on the flywheel face (62° before TDC in
the 20V turbo, 72° in the V8), is used as a reference point. The pin, along with the crankshaft sensor, generates one signal per
crankshaft revolution.
The signals from the crankshaft sensor and
the signal from the Camshaft Position (CMP)
sensor G40 are used for authorization of
sequential fuel injection and ignition timing.
Substitute Function:
(see Glossary). The sensor
No substitute function for the crankshaft
position sensor is available.
On Board Diagnostic (OBD):
The Motronic ECM recognizes a missing
signal after five seconds of cranking or
engine operation, as well as Short to Battery + and Ground. Should the signal fail
after the engine has been started, the
engine will continue to run, based on the
internally calculated cylinder signal after
engine start.
If the Motronic ECM does not receive
this signal, the engine will not start.
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Engine Speed (RPM) sensor G28
Engine speed is registered by a single sensor
located on the transmission bellhousing. The
sensor reads the teeth of the starter ring gear
through a hole in the bell housing.
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 flywheel teeth
cause an alternating current signal to be
generated whose frequency varies with
engine speed.
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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Camshaft Position (CMP) sensor G40
Two major types of camshaft position sensors
are used on Audi 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
(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.
Hall sender
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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 M2.3.2 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.
Dual knock sensors are used on the 5 cylinder
engine, with sensor I responsible for cylinders
1 and 2, and sensor II responsible for cylinders 3, 4, and 5. Knock sensor I is mounted to
the front of the cylinder block and knock sensor II is mounted to the rear.
Audi V8 engines also uses dual knock sensors, sensor 1 for cylinders 1 - 4 (bank 1), and
sensor 2 for cylinders 5 - 8 (bank 2). The sensors are mounted on either side of the engine
block below the exhaust manifolds.
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 M2.3.2 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 M2.3.2 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.
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.
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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.
The oxygen sensor has three wires. The
oxygen sensor heating element receives
ground and battery power, with the third
wire being the sensor signal wire. The
sensor is grounded through the mounting
threads in the exhaust.
The period of time after an engine start
when the oxygen sensor is not at operating temperature, and therefore not used,
is called
dition can occur after either a cold or
warm start. Conversely, engine operation
with a valid oxygen sensor signal is called
closed loop operation.
open loop operation
. This con-
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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Engine Coolant Temperature (ECT) sensor
G62
The engine coolant temperature sensor is an
NTC sensor
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
(see Glossary), mounted in the
Fuel tank ventilation
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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Intake Air Temperature (IAT) sensor G42
The intake air temperature sensor is a
sensor
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:
Substitute function:
(see Glossary), and is mounted in the
The ECM supplies a fixed reference voltage signal to the intake air temperature
sensor and monitors the voltage drop
caused by the resistance change.
Decreasing (colder) temperatures cause
the resistance to decrease; increasing
(warmer) temperatures cause the resistance to increase.
PTC
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 M2.3.2 Component Summary
Barometric Pressure (BARO) Sensor F96
(5-cylinder)
Turbocharged engines are equipped with a
pressure sensing device to signal the ECM
with information referencing atmospheric
pressure which varies from 14.7 psi at sea
level to 12.3 psi or less in mountainous areas.
It is located in the E-box (passenger-side floor),
mounted next to the ECM.
The BARO signal is used to control turbocharger boost pressure at higher altitudes
where lower air pressure (density) can cause
the turbo-charger to overspeed. The signal is
also used to adjust the air/fuel mixture ratio at
engine start-up to compensate for the
decreased oxygen levels at higher altitudes.
Operation:
The BARO sensor measuring chamber is
open to the atmospheric. A piezo-electric
crystal generates a signal that varies with
the changing atmospheric air pressures.
Manifold Absolute Pressure (MAP) sensor
G71 (5-cylinder, component of ECM J220)
The MAP sensor operates in the same manner as the BARO sensor. The difference
being, instead of referencing atmospheric
pressure, a vacuum line is attached to the
intake manifold. This signal is used to provide
the Motronic ECM with information regarding
boost pressure. This is used for pressure regulation.
On Board Diagnostic:
The ECM recognizes Open circuits and
Short circuits.
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Exhaust Gas Recirculation (EGR)
temperature sensor G98 (V8 only)
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 (NOX).
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:
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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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:
Air conditioner compressor Clutch ON
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.
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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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.
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.
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
tor duration
.
injec-
20 valve engine:
Cylinders 1 - 4 fuel injectors N30 - N33
Cylinder 5 fuel injector N83
V8 engine:
Cylinders 1 - 4 fuel injectors N30 - N33
Cylinders 5 - 8 fuel injectors N83 - N86
Motronic fuel injectors are electronically controlled
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.
solenoid valves
(see Glossary). Fuel
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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Power Output Stages N122 and N192, Ignition coils N, N128, N158, N163 and N164
(5-cylinder)
Ignition coil 1 with Power Output Stage
N70, Ignition coil 2 with Power Output
Stage N127 (V8)
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 5-cylinder, for example,
uses five spark plug mounted ignition coils. At
every firing pulse, when the magnetic field
collapses, the spark plug fires.
Substitute Function:
There is no substitute function for the
ignition coils or the power output stages.
On Board Diagnostic (OBD):
The ECM recognizes short circuits to Battery (+) positive.
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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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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
sary).
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:
electronic dashpot
(see Glos-
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.
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Motronic M2.3.2 Component Summary
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 M2.3.2 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, vac-
uum 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.
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Motronic M2.3.2 Component Summary
Substitute function:
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 M2.3.2 Component Summary
Exhaust Gas Recirculation (EGR)
vacuum regulator solenoid valve N18 (V8
only)
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 (NOX).
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:
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 M2.3.2 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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Heated Oxygen Sensor (HO2S)
Control Module J208
Motronic M2.3.2 Component Summary
The oxygen sensor heater helps to bring the
oxygen sensor up to operating temperature
quickly. The ECM controls the oxygen sensor
heater through 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.
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Motronic M2.3.2 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 recognizes 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 M2.3.2 Component Summary
1. Which of the following components
does NOT receive an output signal
from the Motronic M2.3.2 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
M2.3.2 engine management systems
can adapt to variables such as small
vacuum leaks and altitude.
Technician B says that Motronic
M2.3.2 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
4. Technician A says that the Motronic
M2.3.2 ECM retains learned values
when the battery is disconnected.
Technician B says that the Motronic
M2.3.2 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 M2.3.2 fuel injectors operate:
a. Sequentially
b. In groups of two
c. All at the same time
d. None of the above
3. Motronic M2.3.2 engine management
systems store and use learned values.
This process is called:
a. Stoichiometric
b. Adaptive learning
c. Lambda
d. Default value retention
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Motronic M2.3.2 Component Summary
6. Technician A says that all Motronic
M2.3.2 engine management systems
use exhaust gas recirculation.
Technician B says that all Motronic
M2.3.2 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
7. Which of the following statements is
applicable to the Motronic M2.3.2
NOT
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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MPI - Multi Port Fuel Injection
system
System description
MPI (MMS 100 - 300)
The MPI system is a multi port fuel injection
system. The injection quantity and the ignition
timing are continuously adjusted by control
elements (actuators) on the basis of constantly evaluated signals from the transmitters (sensors).
The ECM J192 has four individual harness
connectors with a total of 64 pin terminals,
and is located in the electronics box in the
passenger-side footwell.
The MPI system also has a permanent Diagnostic Trouble Code (DTC) memory used for
On Board Diagnosis. The system can be
tested using the VAG 1551 Scan Tool in
"Rapid Data Transfer mode.
The first MPI system was installed in the Audi
quattro 90 and Audi Coupe. In 1992, the MPI
system was installed on Audi 100 models
(MMS 100), and continued through model
year 1998 (Audi A6 Avant and Cabriolet).
Functionality was continually improved, creating several different versions of the MPI system. These systems include:
MMS 100/200
MMS 300
MMS 311
MMS 400
MMS 410
MMS 411
MMS 412
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MPI (MMS 100 - 300)
MMS 100/200 overview
In 1992, Audi began utilizing the MPI Multi
port Fuel Injection System on their new 100
models equipped with the V6 2.8 liter 2 valve
engine. This car replaced the previous 100
model and was the fourth generation of the
large C class. The latest version of the Audi
designed MPI Motor Management System
(MMS100/200) was used in the V6 engine. It
was similar to the system used on the Audi 90
quattro and Coupe quattro with the 20 valve
engine, with the following changes:
Distributorless ignition system
New style Bosch fuel injectors
Solenoid valve for the intake manifold
change over valve
EGR for 50 states
Single valve for fuel tank ventilation
Inputs - MMS 100 - 300
The ECM receives inputs that are similar to
previous Motronic systems, including the following:
Mass Air Flow (MAF) sensor G70
CO Potentiometer G74
Crankshaft Position (CKP) sensor G4
Engine Speed (RPM) sensor G28
Outputs - MMS 100 - 300
The ECM receives outputs that are similar to
previous Motronic systems, including the following:
Fuel Injectors N30 - 33, N83, N84
Power output stage N122
Ignition coils N, N128, N158
Idle Air Control (IAC) N71
EGR valve N18
Evaporative Emissions (EVAP) canister
purge regulator valve N80
Intake Manifold change-over Valve N156
Fuel Pump relay J17
On Board Diagnostic (OBD)
The ECM continuously monitors the systems
input and output signals. If malfunctions
occur, they are stored in the control units permanent Diagnostic Trouble Code (DTC) memory.
In addition, malfunctions will also be stored if
the knock regulations or oxygen sensor control reach their control limits. On California
models, the control unit also monitors the
operation of the EGR system and will record
malfunctions if they occur.
Camshaft Position (CMP) sensor G40
Throttle Valve Potentiometer G69
Idle switch F60
Knock Sensors (KS) G61, G66
Heated Oxygen Sensor (HO2S) G39 and
G108
Exhaust Gas Temperature sensor G98
86
The MPI system expanded On Board Diagnostic is capable of the following:
Store and display malfunctions from the
permanent DTC memory.
Transmit information through VAG 1551
scan tool using "Rapid Data Mode."
Generate output test signals via output
Diagnostic Test Mode (DTM) of all actuators
(Idle stabilizer valve, fuel injectors etc.
Fuel system
The MPI fuel delivery system operates the
same as the Motronic system (see page 55
for more specific details).
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MMS 100/200 System Components
MPI (MMS 100 - 300)
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MPI (MMS 100 - 300) Component Differences
Input Sensors
The input sensors that differ from previous sytems are detailed in this section.
ECM J192
The ECM J192 has four connectors, with a
total of 64-pins. The individual harness connectors are attached to the ECM using locking tabs, which are released by squeezing the
harness connector while gently pulling the
connector from the ECM.
The ECM processes all inputs and calculates
outputs for ignition timing and injector duration based on control maps.
The ECM has the following diagnostic capabilities:
Read Individual Measuring Values (scan tool
function 09
Rapid data transfer/Blink codes
Individual component monitoring
Coding is accomplished using a coding connector as in the M2.3.2 system.
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MPI (MMS 100 - 300) Component Differences
Mass Air Flow (MAF) Sensor G70
A hot-wire mass air flow sensor is used on
the MMS 100/200 system. It is manufactured
by Hitachi, and is digital (as opposed to the
earlier Bosch sensors which were analog).
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.
Substitute Function:
If a malfunction develops in the MAF
sensor, the signals from the throttle
potentiometer and Engine Speed (RPM)
sensor are used as a substitute in order
to maintain driveability.
On Board Diagnostic (OBD):
The Engine control unit recognizes two
fault conditions of the Mass Air Flow
Sensor; Open and Short to Battery +.
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MPI (MMS 100 - 300) Component Differences
CO Fuel Trim (FT) Potentiometer G74
A Carbon Monoxide (CO) fuel trim potentiometer is installed in the MAF sensor housing.
The CO potentiometer is used to adjust the
idle injection quantity. The MAF Sensor G70
and the CO Fuel Trim (FT) Potentiometer G74
are supplied with battery voltage (terminal 15)
by the Fuel Pump (FP) relay.
Substitute Function:
No substitute function is available.
On Board Diagnostic (OBD):
The ECM recognizes two failures of the
CO potentiometer; Open and Short circuit to Battery +.
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MPI (MMS 100 - 300) Component Differences
Engine Coolant Temperature (ECT) sensor
G62
The coolant temperature sensor is located on
the coolant pipe in back of the left cylinder
head.
The coolant temperature is an NTC sensor
(see Glossary). The coolant temperature information is used by the ECM as a correction
factor for the following:
Cold start enrichment
Correction to injection and ignition
timing for cold engine
Idle speed control
Deceleration fuel shut-off
The engine coolant temperature sensor also
is used to activate certain systems at a predetermined temperature such as, oxygen sensor control, knock control, and exhaust gas
recirculation.
Substitute Function:
If the ECM detects a malfunction in the
coolant temperature sensor or in the wir-
ing, it assumes a temperature of 68°F
(20°C) when the engine is first started.
18°F (10°C) is added per minute of
engine operation until the maximum temperature of 185°F (85°C) is reached.
On Board Diagnostic (OBD):
The MPI system recognizes Open circuit,
Short circuit to Battery +/Ground as well
as implausible signals.
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MPI (MMS 100 - 300) Component Differences
Engine Speed (RPM) Sensor G28
The engine speed sensor is an
sor
(see Glossary). The sensor is located on
the rear, left side of the engine block. It
senses the 135 teeth of the starter ring gear.
The ECM receives one pulse for every tooth
on the ring gear. This sine wave from the
speed sensor is used by ECM to calculate the
ignition firing point and injection point as
determined by engine speed.
Note:
The engine speed sensor position is adjusted
at the factory. Before removing the sensor
bracket, mark the position of the bracket on
the engine block.
Substitute Function:
No substitute function for the engine
speed sensor is available.
On Board Diagnostic (OBD):
The ECM recognizes a missing signal
after five seconds of cranking or engine
operation. If the MPI does not receive a
signal, the engine will not start.
inductive sen-
Crankshaft Position (CKP) Sensor G4
The Crankshaft Position (CKP) sensor is an
inductive pickup
is located on the left side of the engine block.
The sensor is used to identify TDC number
three cylinder.
A notch, 62° before TDC in the counterweight
of the crankshaft for number three cylinder, is
used as a reference point. The notch, along
with the crankshaft sensor, generates one
signal per crankshaft revolution.
The signals from the crankshaft sensor and
the signal from the Camshaft Position (CMP)
sensor G40 are used for authorization of
sequential fuel injection and ignition timing.
Substitute Function:
No substitute function for the crankshaft
position sensor is available.
On Board Diagnostic (OBD):
The ECM recognizes a missing signal
after five seconds of cranking or engine
operation, as well as Short to Battery +
and Ground.
If the MPI does not receive this signal,
the engine will not start.
(see Glossary). The sensor
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MPI (MMS 100 - 300) Component Differences
Camshaft Position (CMP) Sensor G40
The CMP sensor is a
sary). The sensor is located at the end of the
camshaft on the left cylinder head.
The signal from the Camshaft Position (CMP)
Sensor G40 along with Crankshaft Position
(CKP) sensor are used during starting to identify TDC of cylinder number three.
When starting the engine, the ECM triggers
the ignition and sequential injection after
receiving both signals.
Substitute Function:
No substitute functions are available for
the camshaft position sensor.
On Board Diagnostic (OBD):
The ECM recognizes the following malfunctions. Open circuit and Short circuit
to Ground/Battery +.
If the ECM does not receive the Hall signal
the engine will not start.
Hall sensor
(see Glos-
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MPI (MMS 100 - 300) Component Differences
Throttle Position (TP) Sensor G69
The throttle position sensor is a potentiometer connected to the throttle shaft. The ECM
supplies a 5 Volt reference to the sensor and
measures the voltage drop across the potentiometer as throttle valve angle changes. The
TP sensor and Closed Throttle Position (CTP)
Switch F60 are combined in a single housing,
mounted on the throttle body.
The signal supplied to the ECM is used to
determine the position of the throttle valve
and the speed of throttle movement. This
information is used for:
Acceleration enrichment
Full throttle enrichment
The throttle position sensor combined with
the Engine Speed (RPM) sensor is also used
as a substitute signal for Mass Air Flow (MAF)
Sensor G70.
Substitute Function:
No substitute function is available for the
throttle position sensor.
On Board Diagnostic (OBD):
The ECM recognizes the following failures. Open circuit conditions of the throttle position sensor: Open/Short circuit to
Ground, Implausible signals (checked
against MAF signal).
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MPI (MMS 100 - 300) Component Differences
Closed Throttle Position (CTP) Switch F60
The Closed Throttle Position (CTP) switch and
the throttle position sensor are combined into
a single housing on the bottom of the throttle
housing.
The Closed Throttle Position (CTP) switch
closes 1.5° before the primary throttle plate
closes. When the switch is closed, a Ground
signal is supplied to the ECM.
The ECM uses the CTP signal to activate the
following functions:
Idle stabilization
Deceleration fuel shut off with engine
warm and above 1500 RPM. Fuel supply
is reactivated when engine speed falls
below 1200 RPM.
Special ignition map for deceleration
Substitute Function:
No substitute function is available for the
idle switch.
On Board Diagnostic (OBD):
A short circuit to Ground is detected
when the idle switch remains closed
while the TP sensor signal varies.
If the idle switch is not operated once in
ten minutes after the engine is started,
and engine speed is above idle speed,
and open circuit is detected.
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MPI (MMS 100 - 300) Component Differences
Knock Sensors (KS) I and II G61 and G66
On the Audi V6 engine, dual knock sensors
are used. Dual sensors allow for more accurate control of cylinder selective knock control. When knock occurs, the ignition timing is
retarded 3° per crankshaft rotation with a
maximum retard of 12°. After knock has subsided, the ECM advances timing at a rate of
0.33° per revolution until knock occurs again.
Knock sensor I is located on the right cylinder
bank under the manifold and monitors cylinders 1, 2 and 3.
Knock sensor II is located on the left cylinder
bank and monitors cylinder 4, 5 and 6.
The knock sensors can be removed by using
a long 8 mm allen wrench (special tool 3247)
without removing the intake manifold.
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