wiring AUDI A3 1995 8L / 1.G ATW Engine Additional Signals Workshop Manual

24-156

Engine speed signal, checking


Note:
The engine speed signal is output at terminal 37
of the Engine Control Module (ECM). The signal
is used, among other things, for RPM display in
the instrument cluster.

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

- Check following wire connection for open circuit
and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
Instrument cluster

Terminal
37 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations

- Repair open circuit or short circuit if
necessary.
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24-159

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

- Connect VAG1527B voltage tester to sockets 3
(B+) and 54 (VSS) of VAG1598/31 test box.

- Switch ignition on and turn front left wheel by
hand.


LED must blink (very brief blink signal).
If LED does not blink:

- Check following wire connection for open circuit
and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
Instrument cluster

Terminal
54 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations

- Repair open circuit or short circuit if
necessary.
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24-162

- Depress gas pedal completely (swiftly) and then
release it (brief acceleration).


Specified value in display field 4: Indication
jumps for a few seconds from "Compr. ON"
to "Compr. OFF" (compressor is switched off
when vehicle accelerates).
If indications do not resemble description:

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

- Check following wire connection for open circuit
and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
A/C control
head -E87-
Terminal
41 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations

- Repair open circuit or short circuit if
necessary.
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- If there are no malfunctions in the wiring, check
function of A/C system.

Repair Manual, Heating & Air Conditioning,
Repair Group 01; On Board Diagnostic (OBD) of A/C system

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24-163

Wire for crash signal, checking

The Engine Control Module (ECM) receives the
crash signal ("Crash shut-off was triggered") from
the airbag control module.
When the airbag control module sends the crash
signal to the ECM (during an accident or when
output DTM is being performed for the airbag
system), the ECM switches the Fuel Pump (FP)
off. This means that the engine will stop running
but can be started again afterward (e.g. to
remove vehicle from danger).

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

- Check following wire connection for open circuit
and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
Control module for
Airbag -J234-
Terminal
67 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations
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24-164

- Repair open circuit or short circuit if
necessary.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations If no malfunctions are found in wire:

- Check DTC memory of control module for
airbag:

Repair Manual, Body On Board Diagnostic
(OBD), Repair Group 01; OBD of airbag system BAE (basic trigger unit) with side airbag; DTC memory, checking

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24-165

Consumption signal for board
computer, checking


Note:

The consumption signal is calculated by the
ECM from the injection time and directed to the
board computer via terminal 81 of the ECM.
Consumption signal, checking

Electrical Wiring Diagrams, Troubleshooting &
Component Locations
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24-166

Wire for fuel level signal, checking


Note:

The signal helps with cause localization when
certain malfunctions are recognized (e.g.
combustion misfires).
The processed signal enters at terminal 30 of
the ECM and is used to determine the cause of
certain recognized malfunctions (e.g.
combustion misfires).

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

- Check following wire connection for open circuit
and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
Instrument cluster

Terminal
30 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations
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24-168

Test requirement:

Control module coding OK Page 01
-62
.

Test sequence

- Switch ignition off.

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

- Check following wire connection for open circuit
and short circuit to Ground (GND) and B+:

Test box
VAG1598/31
Socket
ABS control module (w/EDL)
-J104-
Terminal
74 Electrical Wiring Diagrams,
Troubleshooting & Component
Locations
If no malfunctions are found in wire:

- Replace ABS control module.
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24-173

Example 1:

From the DTCs stored in the memories, you have determined that control
module 1 is not communicating with control modules 2 and 3.
Electrical Wiring Diagrams, Troubleshooting & Component Locations Control module
DTCs stored in DTC memories:
1
Missing signal from control module 2Missing signal from control module 3
2 Missing signal from control module 1
3 Missing signal from control module 1
- Switch ignition off.
- Disconnect control modules connected across bus wires and check
bus wires for an open circuit. - Replace control module 1 if no malfunctions can be found in bus wires.
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