wiring AUDI A4 1997 B5 / 1.G APB Engine Electronic Engine Power Control Checking Workshop Manual

24-143
Specified value: The EPC warning light should
light up.
If the EPC warning light does not light up:

- Check wire from Engine Control Module (ECM)
to EPC warning light in instrument cluster as
follows: Cause:
EPC warning light is not activated or does
not light up because of an open circuit. Corrective action:
The EPC warning lamp should light up.
If the EPC warning lamp does not light up:
If the warning lamp and the voltage supply are OK: - Switch ignition off
- Connect VAG1598/31 test box . Do not connect engine control module.
- Bridge sockets 1 and 48 on test box
- Switch ignition on.
- Switch ignition off.
- Check whether lamp is burned out and test voltage supply to lamp wiring
diagram.
- Check for open circuit or short circuit in wiring between engine control module
and EPC warning lamp using wiring diagram. Determine and eliminate
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malfunction.
If there are no malfunctions in the wiring to the EPC warning lamp:
Malfunction cause: Engine control module (ECM) faulty Replace Engine Control Module (ECM)
Page 24
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24-144
If EPC warning lamp remains lit for more than 3
seconds (i.e. continuously) when ignition is on,
proceed with test as follows:

- Start engine and allow it to run at idling speed.

Specified value: EPC warning lamp should go
out.
If the EPC warning lamp does not go out:

- Check DTC memory of Engine Control Module
(ECM).
If no DTCs are stored: Cause:
EPC warning light is activated via
short circuit to Ground (GND). Corrective action:
If the specification is not reached: - Switch ignition off
- Connect VAG1598/31 test box . Do not connect engine control module.
- Measure resistance between vehicle Ground and socket 48 on test box. Specified
value: infinity (because the wire should not have any direct Ground connection)
- Determine and eliminate short circuit to Ground in wiring between engine control
module and EPC warning lamp using wiring diagram.
If there are no malfunctions in the wiring to the EPC warning lamp:
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24-152

Note:
If the adaptation process is interrupted by the
control unit, the cause could be one of the
following:

The throttle valve is unable to close completely
(e.g. because of dirt).
The harness connectors (e.g.: at throttle valve
control module) are loose, not properly
connected or the contacts at the connector are
corroded or bent.
Battery voltage too low.
Throttle valve control module or wiring is
faulty.
The engine was started or the accelerator pedal
was depressed during the adaptation process.
Distortion of throttle valve housing (check bolts:
10 Nm)
When the adaptation process is interrupted the
message "Function is unknown or cannot be
carried out at the moment" will appear on the
fault reader display. The adaptation process will
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24-155
The percentage value in display field 1 should
rise steadily, but without covering the full
tolerance range between 3 - 93 %.
The percentage value in display field 2 should
also rise steadily but without covering the full
range of values (in this case 4 - 49 %).
If the display values do not appear as described:

- Check voltage supply and wiring to accelerator
position senders Page 24
-163
.
Observe harness connectors for the following:
Loose connectors, not properly engaged or
corroded.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
- Check accelerator position sensors Page 24
-
159
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24-157

Checking voltage supply to throttle valve
control module

- Disconnect harness connector from throttle
valve control module.

- Switch ignition on.

If the specifications are not obtained, test wiring connections from engine
control module to throttle valve control module Page 24
-158
.
If the readouts match the specifications, test also the signal wires and
activation wires for the throttle valve positioner Page 24
-158
. - Connect hand-held multimeter (voltage range) between the following
sockets on connector:
6-pin connector on wiring harness, socket
Specification
2 + Ground (GND) approx. 5 V
2 + 6 approx. 5 V
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24-158

Checking wiring for voltage, signal and
activation

- Connect VAG1598/31 test box to wiring harness
for engine control module. Do not connect to the
engine control module itself Page 24
-20
.

Test the following wiring connections for open circuits and short to B+ or
Ground (GND).
Electrical Wiring Diagrams, Troubleshooting & Component Locations
If no wiring malfunction is detected:
6-pin connector on wiring harness,
socket
VAG1598/31 test box,
socket
1 92
2 83
3 117
4 84
5 118
6 91
Resistance in wiring: max. 1.5 ohm
- Repair any open/short circuit as necessary.- Replace throttle valve control module.
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24-162

Note:
The value shown in display field 3 should always
be about the double of the value shown in
display field 4.
If the display values do not appear as described:

- Check voltage supply and wiring to accelerator
position sensors Page 24
-163
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24-163

Checking voltage supply of accelerator
position sensors

- Remove storage compartment on driver's
side.

Repair Manual, Body Interior, Repair Group
68


- Disconnect harness connector for accelerator
position sensor.

- Switch ignition on.

- Connect hand-held multimeter (voltage range) between the following
sockets on the connector: 6-pin connector on wiring harness, socket
Specification
2 + Ground (GND) approx. 5 V
1 + 3 approx. 5 V
5 + Ground (GND) approx. 5 V
5 + 4 approx. 5 V
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24-164
If the specifications are obtained:

- Check signal wiring Page 24
-164
.
If the specifications are not obtained:

- Check wiring between Engine Control Module
(ECM) and accelerator position sensors.

Checking wiring

- Connect VAG1598/31 test box to wiring harness
for engine control module. Do not connect to the
engine control module itself Page 24
-20
.

- Check for open circuit and short to B+ or Ground
(GND) in the following wiring connections:

Connector socket
VAG1598/31 test box
Socket
1 72
2 73
3 36
4 35
5 33
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