battery AUDI A3 1995 8L / 1.G ATW Engine Ignition System Workshop Manual

28-1


Ignition system, checking

General notes on ignition system


Note:

The battery should only be disconnected and
reconnected when the ignition is turned off,
since otherwise the Engine Control Module
(ECM) can be damaged.
For the electric components to work properly, a
voltage of at least 12.7 V is required.
It is possible that the control module will
recognize a malfunction and store a DTC during
some tests. After completing all tests and
repairs, DTC memory should therefore be
checked and erased if necessary.
If the engine only starts briefly and then turns
off again after troubleshooting, repair or
checking of the components, it may be that the
immobilizer is blocking the Engine Control
Module (ECM). DTC memory must then be
checked and if necessary, control module must
be adapted.
Pa
ge 1 of 59 I
gnition s
ystem, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.28.1

28-8


If specified value is obtained:
If specified value is not obtained: - Connect multimeter for voltage measurement as follows:Harness connector
Terminal
Measure to
1 Engine Ground (GND)
- Switch ignition on.

Specification: approx. battery voltage
- Check activation of power output stages Page 28
-10
.

- Pull off rubber seal of plenum chamber cover in direction of arrow.
- Remove cover -1- toward front.
Pa
ge 9 of 59 I
gnition s
ystem, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.28.1

28-15


If specified value is not obtained: - Connect multimeter for voltage measurement as follows.Harness connector
Terminal
Measure to
1 Engine Ground (GND)
- Switch ignition on.

Specification: approx. battery voltage
- Switch ignition off.

- Pull off rubber seal of plenum chamber cover in direction of arrow.
- Remove cover -1- toward front.
Pa
ge 16 of 59 I
gnition s
ystem, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.28.1

28-18

Checking voltage supply

If specified value is not obtained:
Electrical Wiring Diagrams, Troubleshooting & Component Locations
If no malfunctions are found in wires: - Connect multimeter for voltage measurement as follows.3-socket relay carrier in E-box, plenum
chamber, position 2
Terminal
Measure to

2 Engine Ground
(GND)
9 Engine Ground
(GND)

Specification: approx. battery voltage
- Check wire connection between central electronics and voltage supply
relay for open circuit.
- Replace central electrics.
Pa
ge 19 of 59 I
gnition s
ystem, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.28.1

28-19

Checking activation

If specified value is not obtained: - Connect multimeter for voltage measurement as follows.3-socket relay carrier in E-box, plenum chamber,
position 2
Terminal
Measure
to

4 B+
- Switch ignition on.

Specification: approx. battery voltage
- Switch ignition off.
- Connect VAG1598/31 test box at wiring harness to Engine Control
Module (ECM), do not connect ECM Page 24
-19
.
Pa
ge 20 of 59 I
gnition s
ystem, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.28.1

28-23


Display fields

1 2 3 4
Display group 004: Intake Air Temperature (IAT), engine at idle
Display xxxx/min xx.x volts
xxx.x C
xxx.x C
Indicated Engine speed
(RPM) Battery
voltage Coolant
temperature Intake Air Temperature (IAT)
Functional
range
-48.0 to 143.0 C
Specified value xxxx/min 12.0 to 15.0 V
80.0 to 110.0 C
From ambient temperature up to 110
C
1)
1) If a temperature is indicated which differs greatly from ambient temperature of sensor, check sensor and sensor wires for
contact resistances and open circuit.
Pa
ge 24 of 59 I
gnition s
ystem, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.28.1

28-32


Display fields

1 2 3 4
Display group 004: Coolant temperature, engine at idle
Display xxxx/min xx.x volts
xxx.x C
xxx.x C
Indicated Engine speed
(RPM) Battery
voltage Coolant temperature Intake Air Temperature (IAT)
Functional
range
-48.0 to 143.0 C

Specified value xxxx/min 12.0 to 15.0
V Temperature value must rise
evenly From ambient temperature up to
110 C
If display field 3 does not have a realistic
indication:

- Disconnect connector at coolant temperature
sensor.

Coolant temperature sensor with square
connector:

- Connect multimeter between terminal 1 and 3 of sensor for resistance
measurement.
Pa
ge 33 of 59 I
gnition s
ystem, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.28.1

28-37

Test requirements:

Fuses for engine electronics OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

Battery voltage at least 12.7 V
Generator OK

Test sequence

- Connect VAG1598/31 test box at wiring harness
to Engine Control Module (ECM), do not connect
ECM Page 24
-19
.

- Switch ignition on.

Note:

The plus voltage supply for the Engine Control
Module (ECM) travels via terminal 3 and 121
(terminal 15) as well as terminal 62 (terminal
30).

Pa
ge 38 of 59 I
gnition s
ystem, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.28.1

28-38

- Connect multimeter for voltage measurement as
follows:

VAG1598/31 test box
Socket
Measure to
1 B+
2 B+
62 Engine Ground (GND)


Specification: approx. battery voltage

- Connect multimeter for voltage measurement as
follows:

VAG1598/31 test box
Socket
Measure to
3 Engine Ground (GND)

- Switch ignition on.


Specification: approx. battery voltage
If specified values are not obtained:
Pa
ge 40 of 59 I
gnition s
ystem, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.28.1

28-39

- Connect multimeter for voltage measurement as
follows:

VAG1598/31 test box
Socket
Measure to
121
1)

Engine Ground (GND)

1) The motronic Engine Control Module (ECM)
power supply relay -J271- continues to direct
current to terminal 121 of the Engine Control
Module (ECM) for up to 15 minutes after ignition
is switched off.

- Switch ignition on.


Specification: approx. battery voltage
If specified value is not obtained:

- Check wire connections.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

-
Check motronic Engine Control Module (ECM)
Pa
ge 42 of 59 I
gnition s
ystem, checkin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU06.28.1