SKODA Self Study Program 16 – OCTAVIA 1.9-ltr./66 kW (TDI) Engine, Fuel Injection and Glow Plug System ssp-016-19-tdi-engine

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„... high output,

For the first time in the
OCTAVIA, Skoda is offering
a modern turbodiesel engine

low fuel
consumption!“

with direct injection.
This engine has an intelligent

engine management system
to provide high output and
low fuel consumption!

2

SP 16-1

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Contents

Technical Data 4

The TDI Engine 5

Highlights 8

System Architecture 12

Position of Components 14

System Overview 16

Sensors 18

Actuators 29

Fuel Metering Control 38

Commencement of Injection Control 40

Exhaust Gas Recirculation 42

Charge Pressure Control 44

Auxiliary Heater System 46

Glow Plug System 47

Emission Characteristics 48

Function Diagram 50

Self-Diagnosis 52

You can find information regarding inspection
and maintenance, setting and repair instructions
in the Workshop Manual .

Service Service Service Service

Service

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Service

3

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Technical Data

Engine data:

Engine code: AGR
Type: 4-cylinder in-line

turbodiesel
Displacement: 1896 cm3
Bore: 79.5 mm
Stroke: 95.5 mm
Compression ratio: 19.5 : 1
Rated output: 66 kW (90 ch) at

4000 rpm

SP 16-2

Max. torque: 202 Nm at

1900 rpm
Mixture formation: Direct injection with elec-

tronically controlled distri-

butor injection pump
Emission control: Exhaust gas recirculation

and oxidation catalytic

convert

The 1.9-ltr. TDI engine achieves its maximum
output of 66 kW (90 HP) at 4000 rpm.

The engine is characterized by a particularly
good torque curve. Maximum torque of 202 Nm
is already available at 1900 rpm.
These engine data reflect the excellent pulling
power of the engine.

P = Output

SP 16-3

4

M = Torque
n = Engine speed

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E

The TDI Engine

– Bosch distributor injection pump VP 37 EDC with 800

bar pump pressure. The distributor injection pump is
preset. The flange is pressed onto the drive shaft and
must not be removed.

Special features of the

1.9-ltr. TDI engine

– Inlet port designed as swirl port. Sets the inducted air

in a swirl motion, which ensures intensive swirling of
the air in the combustion chamber.

– Specially shaped piston bowl (main combustion

chamber).
– Injectors with two-stage fuel injection.
– Charge pressure control.
– Coolant pump installed in cylinder block.
– Coolant thermostat installed in cylinder block.
– Coolant preheated by electric auxiliary heater.
– Alternator freewheeling.
– Exhaust gas recirculation valve in intake manifold.
– Plastic-coated injection pipes as a protection against

corrosion.
– Valve cover gasket vulcanized in place.
– Oil pan with silicone sealant.
– Replaceable oil filter designed as paper cartridge.
– Vacuum pump driven by the camshaft.

Electronic control

The quantity of fuel injected and the injection timing
are controlled with the aid of the electronics to meet
the high demands in terms of fuel consumption and
emissions.

This task is carried out by the

lectronic D iesel C ontrol ( EDC ).
It determines the quantity of fuel and the com­mencement of injection of the distributor injection
pump, controls charge pressure, exhaust gas recir­culation and glow period.

SP 16-4

Diesel direct injection system control unit
J248

5

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

The TDI Engine

Brief description of mechanical components of the TDI

Setting distributor injection pump and toothed belt

The toothed belt drives the

Camshaft gear

Semi­automatic
tensioning
pulley

Coolant pump

Crankshaft
toothed belt pulley

Guide pulley

Injection
pump gear

Guide pulley

SP 16-5

– Camshaft
– Distributor injection pump
– Coolant pump

The required belt arc is achieved by two guide pul­leys, the tension by the semi-automatic toothed belt
tensioning pulley.

Toothed belt setting

Appropriate markings are provided for setting the
timing (crankshaft, camshaft, injection pump posi­tion).

– Crankshaft position

Marking - top dead centre of cylinder 1 - is visible
on the flywheel through the inspection hole of the
gearbox.

Locking drift
MP1-301

SP 16-6

SP 16-7

Note:
When carrying service or repair work on the too­thed belt with the engine removed, align the mar­king on the ribbed V-belt pulley of the crankshaft
with the marking on the toothed belt cover.

– Camshaft position

The correct position is fixed by a new setting
gauge. The exact middle position should be
determined with feeler gauges.
The exact camshaft position is of major
importance for precise timing when fitting on the
toothed belt.

– Injection pump gear

The position of the injection pump is fixed with
the locking drift. The injection pump gear is split
in two. A precision adjustment can be made by
slackening the 3 bolts - arrows -.

Note:
On no account slacken the nut for the hub of the
injection pump.
If this is done, the basic setting of the injection
pump will be altered and cannot be correctly set
again with workshop tools.

The exact procedure is described in the Workshop Manual
for the 1.9-ltr. turbodiesel engine

6

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

The charge air cooler

The charge air cooler cools the inducted air before it
enters the intake manifold. The charge air cooler is
installed between the bumper and right wing and is
force-cooled by the airstream.

Cylinder head gasket

Why is the charge air cooler required?
The turbocharger of the TDI engine heats the induc­ted air, which results in a loss of power of the
engine.
This loss of power is avoided by cooling the inducted
air in the charge air cooler. The density of the air
rises as the air temperature drops. The cylinders are
filled with colder and denser air which is richer in
oxygen, and this in turn results in a further boost in
engine output.

SP 16-8

The cylinder head gasket is made of metal, which is why it is resistant to hig­her temperatures and pressures.
The gasket can also be used in other engines of the 1.9-ltr. diesel engine
range.

Note:
Take into account the difference
in thickness.

SP 16-9

7

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Highlights

Injection nozzles

Two-spring nozzle holder

A gentle rise in pressure in the combustion chamber is required for minimising
combustion noises and reducing the mechanical stresses. In addition, the fuel
should be injected not suddenly, but continuously over a lengthy period.

A two-spring nozzle holder has been developed for the 1.9-ltr. TDI engine with
the aim of achieving soft combustion. This nozzle holder injects the fuel in two
stages.

Stroke 1

Spring 1

Nozzle holder

Spring 2

Nozzle needle

Function

1st (prestroke)
The nozzle holder contains two springs of different thickness. These are matched
to each other in such a way that the nozzle needle is raised only against the force
of spring 1 at the commencement of injection. As a result of the gap produced by
stroke 1, only a small quantity of fuel is pre-injected at a low pressure
(p = 190 bar).
This results in a gentle rise in the combustion pressure and creates the conditions
necessary for igniting the main quantity of fuel.

Stroke 1 +
Stroke 2

Stroke 2

Prestroke Total stroke

SP 16-10

2nd stage (total stroke)
The injection pump constantly supplies more fuel. This results in a pressure rise in
the injection nozzle because the quantity of fuel supplied by the pump is not able to
flow off through the small gap. As a result of this pressure rise, the force of spring 2
is overcome and the nozzle needle raised by stroke 2 to the total stroke. As a
result of the enlarged gap, main injection occurs with the remaining quantity of fuel
at a higher injection pressure (p = 300 bar).

8

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

.

Needle lift sender G80

The injection nozzle of the 3rd cylinder is equipped with a needle lift sender G80 for
detecting the commencement of injection.
The sender monitors the actual moment of opening of the injection nozzle and the
signal is passed to the EDC control unit.
The electronic control unit compares the incoming signal with the map for the com­mencement of injection and analyses the difference

Nozzle holder

Thrust pin

Magnetic coil

SP 16-11

Function

The needle lift sender G80 consists of a
magnetic coil which is supplied with a con­stant current by the control unit. This cur­rent creates the magnetic field in the coil.

A thrust pin is located in the inside of the
magnetic coil, as an extension of the
nozzle needle. The movement of the thrust
pin causes a change in the induced voltage
in the magnetic coil.

The moment of induction of the voltage in
the coil is compared by the control unit with
the top dead centre signal.
The actual commencement of injection is
calculated from this difference. Following
this, the "actual" value for the commence­ment of injection is compared with the "set"
value, and commencement of injection is
corrected accordingly if differences exist.

Substitute function

If the needle lift sender fails, an emergency
running programme is activated. The com­mencement of injection is controlled with
this programme on the basis of a stored
injection map.
In addition, the quantity of fuel injected is
reduced.

9

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Highlights

Return-flow restrictor

The return-flow restrictor is located in the delivery
valve of the injection pump which controls the flow
in the injection pipe to the pump. The purpose of the
return-flow restrictor is to prevent fuel dripping out
subsequently at the injection nozzle and the forma­tion of vapour bubbles in the injection pipe.

Restrictor drilling

Valve plate

Compression
spring

Delivery valve

SP 16-12

Return flow

During the return flow the force of
the compression spring acts on the
valve plate and shuts off the main
passage. The fuel flows only
through the restrictor drilling. This
cushions any pressure wave which
may exist.

SP 16-13

Valve plate

Compression
spring

10

SP 16-14

Fuel delivery

During fuel delivery the valve plate is
lifted off by the fuel pressure and the
restrictor drilling is inoperative. The
fuel flows through the main passage.

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Vacuum pump

The vacuum pump which is required additionally on a die­sel engine for producing vacuum is driven directly by the
camshaft. The vacuum pump consists of a rotor and a
vane. The vane is made of plastic and is able to move on its
mountings.

SP 16-15

Rotor

Air inlet

(Vacuum connection

)

Expansion of space

Rotor

Vane

SP 16-16

Vane

During a rotary movement of the rotor, the vane is pushed
to the outside and the space is expanded. The space is fil­led with air, as a result of which a vacuum is produced at
the air inlet. The vacuum which is produced in the pump is
used by the brake servo unit and the EGR valve.

Contraction of space

As the rotor and the vane continue to rotate, the space
produced again contracts. As a result of this, the inducted
air is compressed and blown off through the air outlet to
the cylinder head. At the same time, a space is produced
again at the top.

Air outlet

SP 16-17

11

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

System Architecture

G71 + G72

G70

N18

N75

The 1.9-ltr. TDI engine is equipped with an electronic engine control unit. All the control
systems of the engine are combined in the control unit.
As a result of the electronic injected quantity control, it is possible to correct the quantity of
fuel injected in line with the air pressure, the air temperature, the coolant temperature and
the fuel temperature. In the past, using mechanical control systems, it was not possible to
allow for these parameters.
Use of the electronic control unit makes it possible to achieve demanding targets such as
reducing fuel consumption and pollutant emissions while at the same time ensuring a high
degree of accuracy over long periods. At the same time, the system is able to react more
rapidly to stresses which may occur at higher engine outputs.

AGR

G62

G28

VP

G80

Q6

G81

N146
N109
N108

G149

12

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Control functions

Injected quantity control

– Calculating the quantity of fuel to be injected from

performance curves
– Start quantity control
– Fuel shut-off on overrun
– Limiting quantity injected if black exhaust is produ-

ced
– Controlling idling speed and limit speed of engine
– Controlling quantity injected for enhancing smooth

running

Injection advance

– Basic setting of commencement of injection accor-

ding to injection maps
– Correction in warming-up phase
– Controlling the moment of injection when engine

started

J248

Servicing of the engine is greatly simpli­fied and the number of operations invol­ved at an inspection is reduced as a
result of eliminating the need to set the
injection pump.

Any faults which occur can be rapidly
detected and easily rectified as a result
of the complete self-diagnosis system.

F/F47

K29

F36

SP 16-18

G79

J366

T16

EGR exhaust gas recirculation

– Map-controlled

Charge pressure limit

– Map control of charge pressure
– Controlled in line with operating state

Auxiliary heater for coolant

– Map control of heating

Glow period

– Map monitoring of glow period
– After-glowing

Self-diagnosis

– Monitoring of sensors and actuators
– Fault memory
– Basic setting
– Diagnosis of actuators
– Emergency functions
– Reading results of measurements with fault reader

V.A.G 1551 or vehicle system tester V.A.G 1552.

Note:
You will find an explanation of the abbre­viated designations of the components in
the chapters on sensors and actuators.

13

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Position of Components

N18

J248

AGR

G71 + G72

Q6

G80

EGR EGR valve
G71 Intake manifold pressure sender
G72 Intake manifold temperature sender
G80 Needle lift sender
J248 EDC control unit
N18 EGR valve
N108 Commencement of injection valve
N109 Fuel cut-off valve
Q6 Glow plugs (engine)

14

N108
N109

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

N75

J359

J360

G70

Q7

G28

G62

G28 Engine speed sender
G62 Coolant temperature sender
G70 Air mass meter
J359 Low heating output relay
J360 High heating output relay
N75 Charge pressure control solenoid valve
Q7 Heating elements (coolant)

SP 16-19

15

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

System Overview

System overview of electronic control of the TDI

The diesel direct injection system control unit J248 makes use of maps and characteristic curves in
order to ensure that the engine is operating optimally in terms of torque development, fuel con­sumption and emission characteristics in every operating situation.

Sensors

Needle lift sender G80

Engine speed sender G28

Air mass meter G70

Coolant temperature sender G62

Intake manifold temperature sender G72
+ Intake manifold pressure sender G71

Brake light/brake pedal switch F/F47

Clutch pedal switch F36

Accelerator pedal position sender G79
+ Idling switch F60
+ Kickdown switch F8

-GF/M40 <

> PBT

Y
N
A

M
R

PIERBURG

E
G

FLOW

7 .18221.01

DURCHFLUSS

074 906 461

Modulating piston movement sender G149

Fuel temperature sender G81

Additional signals

• Air conditioning

• Terminal DF

16

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Diesel direct injection sy­stem control unit J248
with altitude sender F96

Actuators

Glow plugs (engine) Q6
Glow plug relay J52

Heating element (coolant) Q7
Low heating capacity relay J359

Heating elements (coolant) Q7
High heating capacity relay J360

EGR valve N18

Charge pressure control solenoid
valve N75

Glow period warning lamp
K29

Diagnostic connection

SSP 16-20

Quantity adjuster N146

Fuel cut-off valve N109

Commencement of injection
valve N108

Additional signals

• Engine speed signal

• Fuel consumption signal

• Air conditioning

17

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Sensors

Accelerator pedal position sender
G79

Shaft

Spiral spring

Potentiometer

SP 16-21

The determining factor for calculating the required
quantity of fuel to be injected is the position of the
accelerator pedal - the driver input. This is detected
by a sender. The accelerator pedal position sender
G79 is a potentiometer which is installed in the
pedal mounting.
It is operated by means of a short cable. The poten­tiometer passes the respective angle of rotation to
the electronic control unit.
A spiral spring in the sender housing produces a
restoring force which provides the driver with the
impression that he is operating a mechanical acce­lerator pedal.
In addition to the potentiometer, the sender also
accommodates the idling switch F60 and the kick­down switch F8.

Analysis of signal

The electronic control unit calculates the quantity of
fuel to be injected and the commencement of injec­tion from the signal supplied by the sender. In addi­tion, these signals are used for controlling the
charge pressure and for operating the exhaust gas
recirculation.

12 8

18

5 1 2 3

4

6

60

F

SP 16-22

Substitute function

If the sender is faulty, the engine runs at a fast
idling speed of about 1300 rpm.
This therefore enables the customer to drive to the
nearest workshop. The accelerator pedal position
sender G79 does not operate in such a case.

248

24

J

11 23

Self-diagnosis

The fact that the sender signal is not plausible is
stored in the electronic control unit. This signal can
be checked in function "08", Reading measured
value block, display group "002". The figure for the
accelerator pedal position appears in the second
field of the display as a %.

79

G

8

F

/

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

69 67

2

1

J

248

3

SP 16-23

71

Engine speed sender G28

The engine speed is one of the most important
parameters for calculating the quantity of fuel to be
injected and the commencement of injection.
The inductive sender for engine speed G28 moni­tors the angle position of the crankshaft. The sen­der rotor (a disc with four recesses) is mounted on
the crankshaft. The correct position is fixed by a
dowel pin. The distance between two successive
pulses is measured in the electronic control unit.
The momentary value of the position of the cranks­haft is calculated by analysing the four pulses.

Analysis of signal

The signal is used for calculating the quantity of
fuel to be injected and the commencement of injec­tion. The signal supplied by the engine speed sen­der is analysed for performing the functions of
exhaust gas recirculation, preheating of the glow
plug and the signal for the glow period warning
lamp.

Substitute function

If the engine speed sender develops a fault, the
electronic control unit switches over to the emer­gency mode.
The signal supplied by the needle lift sender G80 is
used as a substitute signal. The commencement of
injection is controlled according to the injection
maps while charge pressure and quantity of fuel
injected are reduced. The idling speed monitor, the
fuel shut-off on overrun and the air conditioning are
switched off, as a result of which engine speed is
reduced slightly during brake applications. All in all,
this fault is noticeable from an increase in idling
speed.

Self-diagnosis

Two possible causes of faults are stored in electro­nic control unit:

- Signal not plausible

- No signal

Note:
If, in addition, no signal is supplied by the
needle lift sender, the engine stops.

28

G

SP 16-24

19

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Sensors

Air mass meter G70

-GF/M40 <

> PBT

PIERBURG

GERMANY

FLOW

7 .18221.01

SP 16-25

Hot film

The task of the air mass meter is to determine the
fresh air mass which is supplied to the engine. The air
mass meter G70 is installed in the intake manifold
immediately downstream of the air filter. It measures
the inducted air mass by means of a hot film sensor.
The hot film is heated with a voltage of 12 V.
The inducted air flowing past cools the surface of the
hot film. As a result of the surface being cooled down,
the resistance of the hot film drops. The voltage drop
produced by this change in resistance is analysed as
an equivalent for the temperature and mass of the
inducted air by the electronic control.

52

6

70

G

3 25

Analysis of signal

The result of the measurement supplied by the air
mass meter is used for controlling the percentage
addition of recirculated exhaust gas mass and the
maximum quantity of fuel to be injected.
A smoke map stored in the control unit limits the quan­tity injected if the inducted air mass is insufficient for
clean combustion.

Substitute function

If the air mass meter fails, the charge pressure limit is
reduced and fixed values are set to ensure that the

248

J

50

25

1

engine operates optimally in the part throttle range.
This results in a reduction in engine output.

20

+12V

SP 16-26

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Intake manifold pressure sender G71
and intake manifold temperature sender
G72

The sender is located downstream of the charge air cooler.
Its signal supplies information on the pressure and tempe­rature of the air in the intake manifold. The charge pressure
is additionally corrected by the value for the pressure and
temperature in the intake manifold.

SP 16-27

Analysis of signal

The signals supplied by the senders G71/G72 are used for
limiting the charge pressure and for controlling the auxiliary
heater.

Substitute function

If sender G71 fails, a fixed value is set by the electronic
control unit. This fixed value maintains the charge pressure
control.

If sender G72 fails, the electronic control unit specifies a
value of about 20°C for calculating the charge pressure limit
and for the auxiliary heater function.

Self-diagnosis

J

13

25 39

248

40

The control unit stores two possible faults:
– Short circuit to earth
– Open/short circuit

The intake pressure is displayed in function "08", Reading

2 3

72

G

P

1

SP 16-28

71

G

4

measured value block "010", display field 3.
The temperature of the intake air is displayed in function
"08", Reading measured value block "007", display field 3.

21

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Sensors

Modulating piston movement sender G149

Fixed iron ring

Distributor
injection pump

The modulating piston movement sender G149 monitors the rotation angle of the eccentric shaft of
the fuel metering control in the injection pump. This is a sensor which operates contactlessly. Its
signals are transmitted directly to the electronic control unit. The sender consists of two inductive
pickups, the operating principle of which is based on the differential transformer principle. The use
of contactless pickups ensures that the sender operates properly irrespective of the surrounding
media, so that any water which may be present in the fuel does not produce any falsified result. A
magnetic alternating field is generated along a specially shaped iron core by an alternating voltage.
A moving iron ring is attached to the eccentric shaft and is able to move along the iron core. The
magnetic alternating field changes in accordance with the position of the moving iron ring. This has
the result of inducing and alternating voltage in the coil. The phase shift of the induced voltage rela­tive to the set voltage is taken as a measure for the position of the fuel metering control. Tempera­ture influences can be ignored because both voltages originate from the same sender and are
transmitted over the same wiring system.

Coil with alternating
voltage

Iron core

Moving iron ring

Eccentric shaft

SP 16-29

22

56

57

1 2 3

149

G

248

J

64

SP 16-30

Analysis of signal

The sender signal corresponds to the momentary position of the
fuel metering control. It is used for comparing the "actual position"
of the fuel metering control with the position calculated by the
electronic control unit. If a difference of set and actual position is
determined, the quantity adjuster N146 alters the position of the
fuel metering control accordingly.

Substitute function

If the control unit does not receive a signal from the modulating
piston movement sender G149, the engine is stopped for safety
reasons.

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Fuel temperature sender G81

Distributor
injection pump

Fuel temperature
sender G81

The fuel temperature sender measures the temperature of the fuel in the injection pump.
The result of the measurement is output as a change in voltage to the electronic control
unit.
The temperature of the fuel is a very important factor because the density of the fuel
depends directly on its temperature. The fuel is forced at high pressure through the injec­tion nozzles by a small piston of the injection pump. The temperature of the fuel has to be
known in order to exactly calculate the quantity to be injected and the commencement of
injection. It is possible to calculate the correct values from the known relation between
fuel temperature and density.

Analysis of signal

The quantity of fuel to be injected and the commencement of injection are calculated
from the signal supplied by the fuel temperature sender.

53

76

SP 16-31

Substitute function

If the sender fails, the electronic control unit specifies a

248

J

fixed value as basis for the calculation.

Self-diagnosis

The electronic control stores the following causes of
faults:

7

81

G

4

– Short circuit to earth
– Open/short circuit.

The fuel temperature is displayed in °C in function "08",
Reading measured value block, display group "007",
display field "1".

SP 16-32

23

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Sensors

Coolant temperature sender G62

The coolant temperature sender is located in the coolant connec­tion of the cylinder head. The sender is designed as a resistor
with a negative temperature coefficient (NTC). As a result of the
voltage drop, the momentary value of the coolant temperature is
passed on to the electronic control unit.

SP 16-33

Analysis of signal

The signal for the coolant temperature is incorporated in calcula­ting the quantity of fuel to be injected, the commencement of
injection, the glow period, the quantity of exhaust gases recircula­ted and for controlling the auxiliary heater system.

54

62

G

Substitute function

If there is a fault in the signal, the fuel temperature is used as a
substitute signal. The maximum possible time is used for the glow
period. The auxiliary heater is switched off.

Self-diagnosis

248

J

70

3

1

The following possible causes of faults are stored:

- Short circuit to earth

- Open circuit/short circuit
The coolant temperature is displayed in °C in function "08", Rea­ding measured value block, display group "007", display field 4.

24

SP 16-34

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Altitude sender F96

Altitude sender F96

SP 16-4

The altitude sender is integrated in the diesel direct injec­tion control unit J248. The measurement is carried out
directly in the control unit. The altitude sender contains a
piezo ceramic element. When the piezo crystal is subjected
to a force, it releases a voltage. This voltage is a measure
for the air pressure. The air pressure is in turn dependent
on the geographic altitude, in other words air pressure
drops as altitude increases. The charge pressure and
exhaust gas recirculation are reduced if there is a drop in air
pressure to avoid black exhaust.

Analysis of signal

The electronic control calculates the charge pressure limit
on the basis of the signal supplied by the altitude sender.

Note:
If the altitude sender develops a fault, it cannot be repaired.
The electronic control unit then has to be replaced.

Substitute function

If the altitude sender fails, the charge pressure is controlled
in line with a fixed value.

Self-diagnosis

The electronic control unit stores any faults which occur.
The air pressure is displayed in mbar in function "08", Rea­ding measured value block, display group "010", display
field 2.

25

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Sensors

SP 16-35

Brake pedal switches for diesel
direct injection system F and F47

The switches F and F47 are housed in a module which
is installed directly at the brake pedal. The switch F
operates the brake lights. The switch F47 supplies the
"Brake operated" signal to the electronic control unit.
This, for example, rules out any risk of a simultaneous
brake application and "Full throttle". Switch F is desi­gned as an N.O. contact and switch F47 as an N.C.
contact.

Analysis of signal

Both switches transmit the "Brake operated" signal to
the electronic control unit. The analysis of both signals
provides a double security in the entire system. The
signal is analysed for fuel shut-off on overrun, impro­ving smooth engine running and monitoring the plausi­bility of the sender signals of accelerator pedal and
idling switch.

9

M

10

M

25

M

F

20 9

4

1

+

Substitute function

If one or both switches fails, an emergency pro­gramme is activated which corrects the control of the
quantity of fuel injected accordingly.

Self-diagnosis

248

J

The electronic control unit stores malfunctions in one
or both switches.

The signals supplied by the switches can be checked
in function "08", Reading measured value block, dis­play group "006".

3

47

F

2

+

26

SP 16-36

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Clutch pedal switch F36

The clutch pedal switch F36 is installed directly at the
clutch pedal. The current position of the clutch pedal is
signalled to the electronic control unit by means of this
switch. The switch is designed as an N.C. contact.

Analysis of signal

SP 16-37

The signal of the clutch pedal switch is used to influ­ence the injected quantity control. The quantity of fuel
injected is reduced for a short time in order to improve
smooth running during a gear change.

Substitute function

If there is a fault in the signal, this reduction of the
quantity of fuel injected is not carried out.

Self-diagnosis

Malfunction of the clutch pedal switch F36 is not
stored by the electronic control unit.

Terminal DF of alternator

The signal of terminal DF is analysed only in con­junction with the auxiliary heater. The signal regarding
available charge capacity exists at terminal DF at the
alternator end.

Substitute function

In the event of a malfunction, the auxiliary heater is
switched off in order to avoid any discharge of the bat­tery.

SP 16-38

Self-diagnosis

No plausibility or open circuit are registered as possi­ble malfunctions.

27

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Sensors

Additional signals
Air conditioning (contact 48)

The signal of contact 48 controls the operation of the AC compressor. At the same time, it is
used to increase idling speed in order to avoid any drop in idling speed when the compressor
cuts in.

Self-diagnosis

The signal is not registered in the fault memory of the electronic control unit.
This signal can be checked in function "08", Reading measured value block, display group
"002".

Road speed (contact 43)

The signal at contact 43 is required for monitoring the smooth running of the vehicle. The elec­tronic control unit controls the quantity of fuel injected in line with the vehicle speed. This ensu­res a high degree of ride comfort, particularly if frequent load changes occur. This description
applies only to models fitted with the cruise control system; not presently assigned on the
OCTAVIA.

Self-diagnosis

The electronic control unit registers faults in this signal.
This signal can be checked in function "08", Reading measured value block, display group
"006".

Cable W (contact 45)

Cable W links the electronic control unit to the combination processor in dash panel insert
J218 in which the electronic immobiliser is integrated. The signal of the immobiliser to prevent
unauthorized persons starting the vehicle off, flows along this wire. If the control unit is repla­ced, it is then necessary to enter the new code in the combination processor.

Self-diagnosis

The electronic control unit registers an open circuit in this wire and, in this case, it is not possi­ble any more to start the engine.

28

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Coil
Spring

Armature

SP 16-39

Actuators

Fuel cut-off valve N109

A self-ignition engine can only be switched off by
cutting off the fuel supply. This is done by the fuel
cut-off valve N109.
It is installed in the upper half of the injection pump.
When it is de-energized, it interrupts the fuel supply
to the distributor injection pump. The fuel cut-off
valve is a solenoid valve. The armature is used at
the same time as a blocking valve. If the coil is exci­tated, the armature is attracted, the spring force is
overcome and the fuel is allowed to flow.

Actuation

The fuel cut-off valve is actuated by a contact of the
electronic control unit. When the contact opens, the
power supply is interrupted and the engine stops at
once.

J

77

8

248

N

Substitute function

In the event of a fault, the vehicle no longer opera­tes because the fuel supply is immediately interrup­ted.

Self-diagnosis

A fault is registered by the electronic control unit.
The correct status of the fuel cut-off valve can be
inspected with function "03" - Final control diagnosis.

109

SP 16-40

29

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Actuators

Glow period and warning lamp K29

The glow period and fault warning lamp K29 performs two tasks:
– Indicating the glow period,

a "continuous light" is indicated during the glow period

– Warning of faults which have occurred,

are indicated by a "flashing light".

4

3

1/min x 1000

5

2

1

6

7

SP 16-41

120

100

140

km/h

80

160

60

180

40

200

20

220

240

Faults are only indicated if there is a risk that it is not possible to
continue the journey.

Actuation

The warning lamp is activated by the control unit if the preglow
system is operating or if faults have occurred at the following
components:
– Needle lift sender G80
– Engine speed sender G28
– Modulating piston movement sender G149
– Accelerator pedal position sender G79
– Brake pedal switch F/F47
– Quantity adjuster N146
– Commencement of injection valve N108

Self-diagnosis

Faults of this signal are not stored. The check is carried out with
function "03" - Final control diagnosis.

Coolant system heater elements Q7

The auxiliary heater consists of three heating elements and is
screwed onto the coolant connection fitting of the cylinder head
at the clutch side.

30

SP 16-42

Actuation

If the intake manifold temperature is below about 5°C at the
moment the engine is started, the electronic control unit activa­tes the heating elements Q7 in the coolant circuit through the
relays J359 and J360.
The start temperature is stored. To avoid any discharge of the
battery, one, two or even all three heating elements are supplied
with voltage, depending on the available charge capacity of the
alternator. The alternator features a special connection (terminal
DF) to the control unit for this purpose. The auxiliary heater is
switched off once the coolant has reached a certain tempera­ture. The cut-off temperature depends on the start temperature.
The lower the start temperature, the higher the cut-off tempera­ture.

Self-diagnosis

Faults in the auxiliary heater are not stored. A check of the hea­ting elements and of the relays is conducted with function "03" ­Final control diagnosis.

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Engine glow plugs Q6

Injection nozzle holder

Significantly longer glow plugs are required for the TDI
engine as a result of the geometry of the combustion
chamber. The glow plugs are positioned so that only
their tips project into the combustion chamber. A
quick-lock makes it possible to quickly examine and
replace the glow plugs.

Glow plug

Actuation

SP 16-43

The relay for the glow plugs is operated by the electro­nic control unit. It specifies the preglow period, the
glow period and the afterglow period.

Engine speed from G28 Pin 67

Coolant temperature from G62

Pin 70

Self-diagnosis

Faults in the glow plug system are not stored. A check
of the glow plugs and of the preheating system is con­ducted with function "03" - Final control diagnosis.

Pin 41

K29

J248

Glow plugs

Pin 42

J52

Q6Q6

Bougies de préchauffage

Q6 Q6

Fuse

Glow plug relay

SP 16-44

31

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Actuators

Quantity adjuster N146

Armature

Coil

Shaft

Eccentric ball joint

SP 16-45

The quantity adjuster is installed in the upper half of the injection pump. It converts the
signals received from the electronic control unit into a change in the position of the
modulating piston. This is done by converting the incoming electric signals into defined
movements of the drive shaft with eccentric ball joint based on the electromotive prin­ciple.
The drive shaft is able to perform movements of up to 60° rotary angle. A spring produ­ces a constant restoring force of the drive shaft in the direction of its initial position. The
eccentric ball joint moves the modulating piston back and forward axially on the distribu­tor piston. This makes it possible to completely open the control cross section (cut-off)
or to completely close it (full throttle).

32

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Eccentric ball joint

Leak quantity

Distributor piston

Actuation

The signal for the accelerator pedal position and the signal for engine speed are used in
the electronic control unit as parameters for controlling the quantity of fuel injected. In
addition, the following correction values are incorporated:

Coolant temperature,
Fuel temperature,
Air mass,
Position of clutch pedal switch and
Position of brake pedal switch.

The electronic control calculates a manipulated variable from these data, which is trans­ferred to the quantity adjuster as a voltage.

Modulating piston

SP 16-46

Substitute function

If a fault develops at the quantity adjuster, the engine stops. As a result of the restoring
force of the spring, the drive shaft is moved into the "0" position if the voltage supply fails.
The control cross section of the distributor piston is thus fully opened and the engine
stops.

Self-diagnosis

Any faults which occur are registered in the electronic control unit. The correct function of
the quantity adjuster can be checked in function "08", Reading measured value block, dis­play group "001". The momentary value of the injected quantity is indicated in display field 2.

33

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Actuators

Commencement of injection valve N108

Injection pump

Diesel direct injection control unit
J248

Pressure roller

advanced

retarded

To suction side of
vane cell pump

The commencement of injection valve N108 is installed in the bottom half of the injection pump. It
converts the on/off ratio into a change in control pressure. This change acts on the non-prestressed
part of the injection timing piston.
The valve is a solenoid valve and consists of a piston, a spring and a coil. As a result of the spring
force, the piston shuts off the fuel return flow in the off position. The return-flow opening is opened by
the electronic control unit actuating the solenoid coil of the valve. As a result of the fuel pressure
acting on the piston, which counteracts the force of the spring, an equilibrium of forces is obtained for

each fuel pressure. This equilibrium of forces ensures that the injection timing piston adopts a defi­ned position and thus alters the moment of commencement of injection. The pin is shifted as a result
of the change in position of the injection timing piston. The shift is transmitted to the radially mounted
eccentric disc in injection pump. As a result of the connection between pin and eccentric disc, the tra­vel of the pin is converted into an angle of rotation. As a result, the eccentric disc is rotated either in
the "advanced" or "retarded" direction and the commencement of injection is altered accordingly.

Spring

Pressurized fuel in in­terior of pump

Eccentric disc

Pin

Injection timing piston

Solenoid coil

Spring

Piston

Commencement of injection
valve N108

SP 16-47

Actuation

The signal of the needle lift sender is used as an actual value parameter for calculating the value for
the signal to the solenoid valve. The electronic control transmits a sequence of pulses of a constant
frequency and different phase angle to the solenoid valve.

Substitute function

In the event of a fault, the control of the commencement of injection is deactivated. If the substitute
function is activated, the charge pressure is limited and the quantity of fuel injected reduced in order
to avoid any damage to mechanical components.

Self-diagnosis

Malfunctions of the commencement of injection control are not stored in the fault memory. The com­ponent can be checked in function "03" - Final control diagnosis. A comparison of the calculated
value with a map value is possible in function "08", Reading measured value block, display group
"004".

34

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

To intake port

Intake manifold pressure

To me­chanical charge
pressure control
valve at turboch­arger

SP 16-48

Charge pressure control solenoid
valve N75

This valve limits the charge pressure as a function of
the value supplied by the electronic control unit.
The pressure unit of the mechanical charge pressure
control valve is actuated.
In the off position, the charge air is able to pass freely
at intake manifold pressure through the valve. In the
actuated state, part of the charge air is diverted to the
intake port.

Actuation

The electronic control unit transmits signals to the
solenoid valve which correspond to the charge pres­sure map. A higher or lower intake manifold pressure
exists at the charge pressure control valve of the tur­bocharger by opening and closing the valve accordin­gly.

J

15

2

1

+12V

SP 16-49

248

N

75

Substitute function

In the event of a fault, the pressure is limited to 0.75
bar by the mechanical control.

Self-diagnosis

A fault in the charge pressure control solenoid valve
N75 is not stored by the electronic control unit. A fault
in the charge pressure control, however, is stored.
Correct operation can be checked in function "03" ­Final control diagnosis.
The set pressure can be read in function "08", Rea­ding measured value block, display group "011", dis­play field 2 and the actual pressure in display field 3.
Correct operation of the system can be checked by
comparing both values.

35

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Actuators

Exhaust gas recirculation valve N18

The exhaust gas recirculation valve converts the
signals supplied by the electronic control unit into a
control vacuum for the mechanical EGR valve.
In the off position, the valve shuts off the vacuum con­nection to the EGR valve. If a voltage is supplied, the
valve opens the vacuum connection. The exhaust gas
recirculation valve permits very accurate control of the
EGR valve.

29

SP 16-50

248

J

2

18

N

1

Actuation

The coil of the valve is supplied with a voltage of con­stant frequency. The pulses supplied by the electronic
control unit are converted into a mechanical move­ment of the armature.

Substitute function

In the event of a fault, exhaust gas recirculation is
stopped, which does not have any effect on vehicle
handling.

Self-diagnosis

Failure of the exhaust gas recirculation valve is not
stored by the electronic control unit. Proper operation
can be checked in function "03 - Final control diagno­sis".
The percentage degree of opening of the EGR valve is
indicated in function "08", Reading measured value
block, display group "003", display field 4.

36

+12V

SP 16-51

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Additional outputs

Fuel consumption (contact 18)

The electronic control supplies a signal regarding fuel consump­tion to the dash panel insert. The exact consumption is calculated
from the position of the modulating piston.
The multifunction display analyses the signal and indicates it as a
consumption over 100 km.

SP 16-4

SP 16-4

Self-diagnosis

Faults of this signal are not stored. The fuel consumption in litres/
hour can be read in function "08", Reading measured value block,
display group "05", display field 3.

Engine speed (contact 6)

The electronic control unit supplies a signal of the engine speed to
the combination processor in the dash panel insert J218. This
signal is required, for example, for indicating engine speed, dyna­mic oil pressure etc.
In the event of a fault, these readouts then no longer operate. The
fault is not stored.

37

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Fuel Metering Control

Engine speed sender G28

Air mass meter G70

Coolant temperature sender
G62

Brake pedal switch F/F47

Clutch pedal switch F36

Accelerator pedal positi­on sender G79
Idling switch F60

Modulating piston mo­vement sender G149
Fuel temperature sen­der G81

Additional signal

Diesel direct injection system control
unit J248

-GF/M40 <

> PBT

PIERBURG

GERMANY

FLOW

7 .18221.01

DURCHFLUSS

074 906 461

Quantity adjuster N146

SP 16-52

The electronic control unit controls the quantity adjuster as a function of the parameters of
quantity injected, engine speed, engine torque, ride comfort and starting. Taking a stored

map value as the basis, the quantity of fuel injected is further specified by various values
supplied by sensors. The following sensor signals flow into the control unit for the quantity
adjuster:

– Accelerator pedal position – Air mass
– Idling switch position – Modulating piston position
– Coolant temperature – Brake pedal position
– Fuel temperature – Clutch pedal position
– Engine speed – Road speed signal

Functions performed

The following fixed values are used for controlling the quantity of fuel injected:
– Map value for quantity injected
– Control of idling and full throttle speed
– Fuel cut-off on overrun
– Start quantity control
– Smoke limiting
– Active jerk control

38

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unless authorised by ŠKODA AUTO A. S. ŠKODA AUTO A. S. does not guarantee or accept any liability

with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Commencement
of injection

Fuel mass

Engine
speed

SP 16-53

Map value for quantity injected

The basis for the signal transmitted to the
quantity adjuster, is a value which is taken
from a map. This map signal is modified by
individual correction factors in order to adapt
the quantity of fuel injected as accurately as
possible. This signal for the modulating
piston travel is used as confirmation and a
correction value for actual injection.

Control of idling and full throttle speed

Values for idling and full throttle speed are stored in the control unit. Full throttle speed is
altered as a result of engine temperature, the connection of electric loads and of the AC
compressor. Control of idling speed begins with the sampling of the engine speed value
from a map, which also takes into account the coolant temperature.
This map value is compared with the actual engine speed. The required quantity to be
injected is calculated from the difference. Maximum engine speed is always constant,
being about 4900 rpm. Once this engine speed has been reached, the quantity injected is
progressively reduced. Once engine speed drops, the quantity injected is again increased.

Fuel shut-off on overrun

The fuel shut-off on overrun shuts off the fuel supply completely to the injectors. This
function is always performed once idling speed rises to more than 1300 rpm without the
accelerator pedal having been depressed or the brake pedal operated.

Start quantity control

The electronic control unit increases the quantity injected when the engine is started. The
map values for the quantity injected are increased in line with the coolant temperature.

Fuel mass

Smoke map

The actual quantity injected is determined in accor­dance with the stored smoke map. If the air mass is
too low, the quantity injected is reduced to such an
extent as to prevent any black exhaust.

Air mass

Engine
speed

SP 16-54

Active jerk control

The active jerk control (AJC) makes it possible to
avoid the occurrence of uncomfortable vibrations of
the vehicle in the longitudinal axis.

39

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Commencement of Injection Control

Needle lift sender G80

Engine speed sender G28

Coolant temperature sender G62

Diesel direct injection system control
unit J248

Commencement of injection
valve N108

SP 16-55

Commencement of injection influences a variety of engine properties such as starting cha­racteristics, fuel consumption and exhaust emission. Programmed commencement of injec-

tion maps take into account these interdependent factors.
The task of the commencement of injection control is to determine the correct moment for
supplying fuel to the injectors. The control loop assures the high accuracy which is required
for commencement of injection.

Functions performed

The following functions are performed by the commencement of injection control:
– Calculating the commencement of injection according to the map values
– Correcting the commencement of injection in the warming-up phase
– Controlling commencement of injection at engine start and during overrun

40

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Commencement
of injection

Calculating the map value for commencement
of injection

The programmed commencement of injection
maps are used as a basis for calculating the com­mencement of injection. The actual commence­ment of injection is detected directly at the
injector, by the needle lift sender G80. This mea­surement is compared with the map value. Any
difference results in a change in the actuation of
the solenoid valve at the injection advance. The
actuation can be continuously changed until the
control variation has reached the value "zero".

Fuel mass

Fixed value control in warming-up phase

The commencement of injection is controlled in accordance with fixed values during
engine starting and the warming-up phase.
The electronic control unit corrects the commencement of injection in line with the coo­lant temperature.

The commencement of injection is shifted toward the "retarded" direction as the coo­lant temperature drops. In contrast, the commencement of injection is shifted toward
the "advanced" direction as engine temperature rises. This contributes to improving
the ignition properties of the fuel at low temperatures.

Commencement of injection control during starting

The moment of commencement of injection when the engine is started is likewise con­trolled as a function of the coolant temperature. The commencement of injection is
advanced in order to improve engine starting.

Engine
speed

SP 16-53

41

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Exhaust Gas Recirculation

J248

G70

N18

A

The concentration of pollutants in the exhaust is reduced as a result of the
exhaust gas recirculation system EGR. The TDI engine operates at higher
combustion temperatures than an engine with a prechamber. High combu­stion temperatures and the air excess produce a higher oxides of nitrogen
content (NOx) in the exhaust. This characteristic has an even more detri­mental effect at low engine speeds. As a result of the EGR system, exhaust
portions are added to the intake air. This reduces the air excess during
combustion. As a result of the reduced air excess, the combustion tempera­ture remains low and the output of oxides of nitrogen is reduced. The map
value limits the quantity of exhaust gases which are recirculated in line with
the emitted mass of hydrocarbons (HC) and carbon monoxide (CO). A high
proportion of recirculated exhaust gases, however, results in a deterioration
in engine output.

42

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G72

AGR

VP

G62

G28

Air mass

Engine speed

Fuel mass

SP 16-57

Control of exhaust gas recirculation

The value for controlling the quantity of exhaust gases which are
recirculated is calculated from a map value as a function of the
values for the inducted air mass, engine speed and the quantity
of fuel injected.
The quantity of fuel injected and engine speed determine in the
map the quantity of exhaust gases which are recirculated.
The control is activated only once engine temperature has
increased to more than 50°C.
The exhaust gas recirculation system remains switched off at a
lower temperature.
Exhaust gas recirculation is only active at engine speeds of less
than 3000 rpm as the oxides of nitrogen level is drastically redu­ced at higher engine speeds. This effect is the result of the shor­ter combustion times and lower air excess.
Once the quantity of recirculated exhaust is determined, the elec­tronic control unit converts the value into an equivalent signal.
This signal is used for accurately meeting the quantity of exhaust
and in turn contributes to avoiding environmental pollution.
The exhaust gas recirculation valve (solenoid valve) controls the
mechanical EGR valve.

SP 16-56

A Charge air cooler
EGR EGR valve
G28 Engine speed sender
G62 Coolant temperature sender
G70 Air mass meter
G72 Intake manifold temperature sender
J248 EDC control unit
N18 Exhaust gas recirculation valve
VP Vacuum pump

43

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Charge Pressure Control

F96

J248

G70

A

The pressure unit B at the charge pressure valve C is pressurized by the charge
pressure control solenoid valve N75. Valve N75 is supplied with electrical
signals by the electronic control unit. This enables the charge pressure to be
influenced in accordance with a map.
Temperature and pressure in the intake manifold are monitored by the intake
manifold pressure and temperature sender G71/G72. Differences from the set
point are adjusted accordingly. The temperature is monitored because of the
influence it has on the density of the air. The charge pressure map is corrected
in line with the air pressure by the altitude sender F96 so that the engine is
always supplied with approximately the same air mass. From an altitude above
MSL of about 1500 metres, the charge pressure is reduced in order to prevent
the turbocharger overrevving.

N75

B

C

44

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G71 + G72

Control of charge pressure

The charge pressure is controlled by altering the on/off
ratio, the mean pressure being controlled in combination
with the atmospheric pressure. The on/off ratio is formed
by comparing the sensor signal and the map value. The
charge pressure control solenoid valve is actuated with
this signal. This valve opens or shuts off the flow of charge
air to the pressure unit. If a high air pressure is supplied to
the pressure unit, it opens a flap in the turbocharger hou­sing. The exhaust gases flow through this flap directly to
the exhaust without passing through the turbocharger.
The charge pressure is controlled in line with the altitude
above MSL and the air temperature.
As the air pressure drops, the charge pressure is reduced
in order to prevent any damage to the turbocharger.

A Charge air cooler
B Pressure unit
C Charge pressure valve
F96 Altitude sender
G70 Air mass meter
G71 Intake manifold pressure sender
G72 Intake manifold temperature sender
J248 EDC control unit
N75 Charge pressure control solenoid valve

SP 16-58

45

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Auxiliary Heater System

Terminal DF

Large heating capacity
relay J360

Heating elements
for coolant Q7

Intake manifold pressure
sender G71 and temperature
sender G72

Coolant temperature
sender G62

Diesel direct injection
system control unit J248

Low heating capacity
relay J359

SP 16-59

As a result of the high efficiency of the TDI engine, only a very slight amount
of heat is dissipated to the coolant. The coolant is heated electrically by the
auxiliary heater if the outside temperature is low.
An alternator with a higher capacity is installed in order to ensure that ade­quate capacity is always available.

Activation

The auxiliary heater is operated in line with the coolant temperature and out­side temperature. The auxiliary heater is switched on if the coolant tempera­ture is below 5°C. It remains in operation for a period depending on the start
temperature.

The heating capacity is connected in accordance with the available alternator
capacity. The output rating is measured for this purpose at terminal DF. The
auxiliary heater is switched on through the relay J359 and J360. One, two or
three heating elements can be connected as necessary.

46

G72

G62

DF

Pin 13

Pin 54

Pin 22

J248

Pin 34

Pin 17

J360

J359

Q7

Q7

Q7

SP 16-60

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Engine speed sender G28

Glow Plug System

Coolant temperature sender G62

A high pressure and high temperature are produced in the combustion chamber during the
compression phase. This has a major impact on the combustion process. The heat dissipa­tion is low as a result of the small surface area of the combustion chamber. Preglowing is
only necessary at low temperatures.
A basic distinction is made between three glow phases:

– Preglow period
– Glow period
– Afterglow period

Controlling the system

The glow plug system is controlled by the electronic control unit. Preglowing is activated only
if the coolant temperature is below +10°C.
The preglow period is all the longer, the colder the coolant.

Diesel direct injection system
control unit J248

Glow plug relay
J52

Glow plugs Q6

SP 16-61

Preglowing is followed by a glow period of 5 seconds.
Afterglowing is activated at coolant temperatures below +20°C when the engine is started for

a period of about 30 seconds. In total, an afterglow period of 90 seconds is possible, depen­ding on the coolant temperature. Afterglowing is switched off once engine speed is greater
than 2500 rpm.

47

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Emission Characteristics

Pollutants in the exhaust

The most frequent pollutants which occur in the exhaust of diesel engines will already be familiar to
you from the information supplied regarding the 1.9-ltr. naturally aspirated diesel engine. The speci­fic characteristics of a TDI engine in respect of pollutants, in particular oxides of nitrogen (NOx), is
explained in the section on exhaust gas recirculation.

The 1.9-ltr. TDI engine features a wide variety of measures aimed at reducing pollutant level, and
betters the exhaust limits which have been in effect since 1996 while at the same time achieving
excellent fuel economy.

The measures which have been implemented with the aim of reducing the pollutants in the exhaust
and how they interact with each other, are explained in detail below.

Reducing pollutants

Measures which are appropriate for reducing the formation of particulates and hydrocarbons (HC),
have the effect of increasing the share of oxides of nitrogen. If oxide emissions are to be cut, it is
then necessary to accept higher levels of the other exhaust elements, and at the same time fuel con­sumption will also be greater.

The lowest possible exhaust emissions was one of the principal criteria as early as the design phase
of all the components involved in the combustion, such as

Injection nozzle,
Piston bowl,
Combustion chamber geometry.

The improvements to the engine management system also have contributed to optimising the com­bustion process.

The main influencing factors are commencement of injection, exhaust gas recirculation and oxi­dation catalytic converter.

Influence of commencement of injection

If the commencement of injection is retarded, it is possible to reduce the level of oxides of nitrogen in
the exhaust. The consequence of this is that engine output is reduced and the level of hydrocarbons
(HC) and particulates increases. These exhaust elements can be improved by fitting a catalytic con­verter. The result of these measures is that the fuel consumption is some 4 % higher.

Influence of exhaust gas recirculation (EGR)

By recirculating the exhaust gases into the combustion chamber it is possible to reduce the oxygen
content. The result of this measure is a reduction in the emission of oxides of nitrogen, although this
may bring about an increase in particulate emissions in certain operating conditions.

48

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Oxidation catalytic converter

A major part of the gaseous pollutant emissions (HC, CO) and particulates are converted in the cata­lytic converter into carbon dioxide (CO
The oxides of nitrogen (NO

x) cannot be converted by the catalyst.

The influence of various design measures on exhaust emissions and the relationship to fuel
consumption, is shown in the diagram below:

250%

200%

150%

2) and water vapour.

1,9 l

TDI

100%

50%

0%

Consumption-

optimised engine

HC

Retarded
commencement
of injection

CO NOx Consumption

Note:
The exhaust emission levels shown on the diagram are relative,
and not absolute figures.

Diesel fuel itself has a decisive influence on clean combustion.
A reduction in the sulphur content from the present 0.13 percent by volume to

0.05 percent by volume (development objective) has the effect of reducing
particulate emissions by seven percent.

Retarded commence­ment of injection and
EGR

Particulates

Retarded commence­ment of injection with
EGR, catalytic converter

SP 16-62

49

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Function Diagram

The function diagram represents a simplified current flow diagram and shows how all the system
components for controlling the diesel direct injection system are interlinked.

Components

A/+ Battery positive
F Brake light switch
F8 Kickdown switch
F36 Clutch pedal switch
F47 Brake pedal switch
F60 Idling switch
G28 Engine speed sender
G62 Coolant temperature sender
G70 Air mass meter
G71 Intake manifold pressure sender
G72 Intake manifold temperature sender
G79 Accelerator pedal position sender
G80 Needle lift sender
G81 Fuel temperature sender
G149 Modulating piston movement sender
J52 Glow plug relay (engine)
J248 Diesel direct injection system control unit
J322 Diesel direct injection system relay
J359 Low heating capacity relay
J360 High heating capacity relay
N18 Exhaust gas recirculation valve
N75 Charge pressure control solenoid valve
N79 Crankcase breather heating element
N108 Commencement of injection valve
N109 Fuel cut-off valve
N146 Quantity adjuster
Q6 Glow plug - engine
Q7 Coolant system heating elements
S... Fuses

30
15

30

J 322

S 234
10A

N108

N75

15

79

52 50127 25

G70

5

A/+

S131
50A

J360

J359

N18

Q7

29

17

13 39

G72

34 33

40

P

G71

12

8 24 11

F60/F8 G79

87

85

A

Q7

23

Additional signals

A Brake lights
B Kickdown signal
C Accelerator pedal position
D Engine control signal (only with automatic gearbox)
E Envisaged for cruise control system (CCS)
F Engine speed signal
G AC compressor cut-off
H AC compressor standby (increase in idling speed)
J Glow plug warning light
K Fuel consumption signal
L Wiring for diagnosis and immobiliser
M Terminal DF
N Combination processor in dash panel insert

50

31

Colour coding/Legend

= Input signal
= Output signal
= Battery positive
= Earth

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J52

30
15

30

86

4

85

87

S13
10A

S243
15A

C

B

F

F47

N79

F36

B146

D

9

20 46 44 7 36 35 21

77 6967 71 55

J248

62 51 22

45

18 41 48 16642

N109

G28

G80

M

K H

N

J

L

S229
15A

E

10

19 47 54 70

2

28 76 53 64

G81

F

G

56 57

G149

S232
10A

G62

806659

54

N146

A/+

S132
50A

Q6

31

SP 16-63

B146 = Positive connection in

interior wiring loom

51

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with respect to the correctness of information in this document. Copyright by ŠKODA AUTO A. S.�

Self-Diagnosis

Self-Diagnosis and Safety Concept of the TDI with Electronic Diesel
Control - EDC

D I A G N O S I S

The control unit carries out the following functions when driving:
– Comparison of the measurements supplied by the sensors for plausibility.
– Monitoring the electrical and mechanical operation of the actuators.

This is done by conducting a set/actual value comparison.
The results have to satisfy certain fixed requirements.

– Monitoring the state of the electrical plug and cable connections for open circuits

and short circuits.

If a fault occurs in the system, the EDC reacts in stages in accordance

Stage 1: If sensors with correction functions fail, the system continues to operate

with fixed substitute values or adopts analysable information from other
sensors.
The driver is usually unaware of this and the fault is detected during the
Annual Inspection.

Stage 2: More significant faults which can result in failure of subfunctions, result in a

reduction in engine output. The driver is advised of this by the glow period/
warning signal lamp flashing.

Stage 3: If the driver can no longer influence the power output of the engine with the

accelerator pedal, the EDC controls the engine into the fast idling mode.
This enables the vehicle to be moved out of flowing traffic.

with the significance of the fault.

R E A C T I O N

Stage 4: If reliable operation of the engine is no longer assured, the engine is swit-

ched off by the quantity adjuster. If the fault does not allow the engine to be
switched off with the quantity adjuster, it is then switched off by means of
the fuel cut-off valve (redundancy).

52

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The diesel direct injection system control unit features a per­manent fault memory. This makes it possible to check faults
which have occurred during earlier starts. This is a reliable
means of rapidly detecting the causes of faults. Self-diagnosis
of the electronic control unit is conducted in operating mode
"1" - TEST OF VEHICLE SYSTEMS.

The faults are analysed with the vehicle system tester V.A.G

1552. All the coloured sensors/actuators are monitored.

-GF/M40 <

> PBT

Y
N

A
M
R

PIERBURG

E
G

FLOW

7 .18221.01

DURCHFLUSS

074 906 461

1

2

3

4

5

6

7

8

9

C

O

HELP

Q

V.A.G.

1552

SP 17-29

Pin 48

DF

Functions of self-diagnosis:
Address word "01" - Engine electronics

Note:
If the address word "00" - automatic test sequence - is selected, all the control
units of the vehicle with a diagnostic capability are interrogated.
The control unit version and the fault memory are displayed.

120

4

100

3

2
1

140

1/min x 1000

km/h

80

5

160

60

180

6

40

200

20

220

7

240

SP 16-65

01 - Interrogating control unit version
02 - Interrogating fault memory
03 - Final control diagnosis
04 - Basic setting
05 - Erasing fault memory
06 - Ending output
07 - Coding control unit
08 - Reading measured value block
09 - Reading individual measured value
10 - Adaptation

53

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Self-Diagnosis

Function "01":
Interrogating control unit version

Part number of
control unit

Function "02":
Interrogating fault memory

Note:
Faults which occur sporadically are
erased again after 40 starts if they
have not re-occurred.

This function enables the control unit versions to be inter­rogated. This function is used to retrieve the stored data of
the control unit which is being examined.

The illustration shows the data which appear in the display
of the vehicle system tester V.A.G 1552 and the meaning:

Displacement
of engine

Type of
engine

Control unit

Software version
of control unit

028906021BT 1.9 l R4 EDC SG DOP
Coding 00000 WSC 00845

Coding of control unit

Interrogating the fault memory makes it possible to read all
the faults which have occurred during driving. A number of
these faults are indicated by the glow period warning lamp
flashing. When the fault memory is read, it is possible to
determine the component or signal which is faulty. A fault
code is displayed which corresponds to the type of fault
which exists. An explanation of this fault code is given in the
Workshop Manual, where you can also find the possibilities
for rectifying the faults.
The following faults are possible:

- Short circuit or short to earth

- Open circuit

- Implausible signal.
The readout in the display is able to distinguish between
permanent faults and faults which occur sporadically. Spo­radic faults are identified at the end of the second line of the
display with /SP. The illustration below provides an
example:

Workshop code

SP 16-66

Fault code

Element or signal causing the fault

00522 Coolant temperature sender - G62

Short circuit to earth /SP

SP 16-67

Type of fault

54

Sporadic or permanent fault

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Function "03":
Final control diagnosis

This function makes it possible to check all the actuators,
their operation and function. Activation is checked with the
engine idling. The engine stops if the fuel cut-off valve is
actuated. The actuators are operated each for 30 seconds.
The period of the test can be extended by using the cursor
keys. The actuators are checked in the following sequence:
– Commencement of injection valve N108
– Exhaust gas recirculation valve N18
– AC compressor, standby
– Fuel cut-off valve N109
– Charge pressure control solenoid valve N75
– Glow plug relay J52
– Glow period warning lamp K29
– Low heating capacity relay J359
– High heating capacity relay J360
To repeat final control diagnosis, switch off ignition for 20
seconds.

Function "04":
Basic setting

The commencement of injection solenoid valve N108 is acti­vated constantly in function "04". As a result, injection is
retarded up to its maximum. The fuel temperature and angle
of advance are read for conducting a dynamic test of fuel
injection. These values should be compared with the values
in the table in the Workshop Manual. It is then possible to
calculate the correct advance angle of the injection pump.
The following illustration shows these values:

System in basic setting

43 34 0 18 15 114 77 132 155 109

Commencement of
injection

SP 16-68

Fuel temperature

55

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Self-Diagnosis

Function "05":
Erasing fault memory

Function "08":
Reading measured value block

Function

Read measured value block
900 rpm 2.5 mg/H 0.720 V 88.2°C

This function erases all faults which do not exist at that
moment. If a fault remains in the memory during erasing, a
readout appears in the display to the effect that the fault has
not been erased. The fault which was not erased is then
displayed.

The measured value block is used for testing the vehicle. If
this measured value block is selected, it is then necessary
to specify the group to be displayed. There are a total of 15
groups, arranged from 001 to 015.

If display group 001, for example, is selected, the following
readout appears in the display of V.A.G 1552:

Display field

The table overleaf shows the meaning of the figures which appear in the individual display groups.

1

2 3 4

SP 16-69

56

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Table of readouts which appear in the display

Display
group 1 2 3 4

001

002

003

004

005

006

007

008

009

010

011

012

013
014

015

Display field

Engine speed

xxxx rpm

Engine speed

xxxx rpm

Engine speed

xxxx rpm

Engine speed

xxxx rpm

Engine speed

xxxx rpm

Road speed

xxxx km/h

Fuel temperature

xxx.x °C

Engine speed

xxxx rpm

Engine speed

xxxx rpm

Inducted air quantity

xxx mg/Stroke

Engine speed

xxxx rpm

Vacant

Injected quantity difference

Cylinder 4 to Cylinder 3

x.xx mg/Stroke

Vacant Vacant Vacant Vacant

Engine speed

xxxx rpm

Quantity injected

xx.x mg/Stroke

Accelerator pedal position

0-100 %

Set inducted air quantity

xxx mg/Stroke

Set commencement of injection

xx.x° B (A) TDC

Start quantity

xx.x mg/Stroke

Xxx Clutch

xXx Brake F

xxX Brake F47

Vacant

Injected quantity driver input

xx.x mg/Stroke

Injected quantity road speed

control

xx.x mg/Stroke

Air pressure

xxxx mbar

Set charge pressure

xxxx mbar

Glow period

xx.xx

Injected quantity difference

Cylinder 2 to Cylinder 3

x.xx mg/Stroke

mg/Stroke

Sender voltage modulating

piston movement

x.xx V

Operating state

111 AC compressor on

010 Idling switch closed

100 Idling speed increased

Actual inducted air quantity

xxx mg/Stroke

Actual commencement

of injection

xxx mg/Stroke

Actual commencement

of injection

xx.x° B (A) TDC

Vacant

Intake air temperature

xxx.x °C

Injected quantity limit

torque map

xx.x mg/Stroke

Injected quantity limit

automatic gearbox

xx.x mg/Stroke

Charge pressure

xxx mbar

Actual charge pressure

xxxx mbar

Supply voltage control unit

xx.x V

Injected quantity difference

Cylinder 1 to Cylinder 3

x.xx mg/Stroke

Consumption l/h Calculated quantity

Coolant temperature

xxx.x °C

Coolant temperature

xxx.x °C

On/off ratio EGR valve

0-100 %

Excitation commencement of

injection valve

0-100 %

Coolant temperature

xxx.x °C

Version with cruise control

system

xxx

Coolant temperature

xxx.x °C

Injected quantity limit smoke

On/off ratio charge pressure

map

xx.x mg/Stroke

Sender voltage modulating

piston movement

x.xx V

Accelerator pedal position

0-100 %

control valve

0-100 %

Coolant temperature

xxx °C

Vacant

mg/Stroke

Note:

You can find the specified values in the Workshop Manual
SKODA OCTAVIA - 1.9-ltr./66 kW (TDI) Engine, Fuel Injection and Glow
Plug System

!

57

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58

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The TDI Engine

– Engine Code AGR –

SP 16-70

... CAN ALSO
RUN ON
BIODIESEL!

59