wiring diagram AUDI A8 1995 D2 / 1.G AHA Engine Auxiliary Signals Checking Workshop Manual

24-164


Auxiliary signals, checking

Signal from A/C compressor, checking


Required special tools and test equipment

VAG1551 or VAG1552 Scan Tool (ST) with
VAG1551/3 adapter cable
VAG1598/22 test box
Multimeter US1119 (Fluke 83 or equivalent)
VW1594 connector test kit
Wiring diagrams

Test conditions
A/C functions OK
A/C is switched off
Vehicle at room temperature-above 15 C
(59 F)

No malfunctions stored in Diagnostic Trouble
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Continuation
If the displayed values are NOT OK:

- Connect VAG1598/22 test box to ECM harness
connector page 01
-67
.

- Check wiring for open circuit, short circuit to B+
or short circuit to Ground between ECM/test box
terminal 8 and either A/C control head -E87- or
Transmission Control Module (TCM).

Electrical Wiring Diagrams, Troubleshooting &
Component Locations binder If the wiring is OK:

- Check function of A/C control head -E87-.

Repair Manual, Heating & Air Conditioning,
Repair Group 01


- Carry out electrical testing of automatic
transmission.
Repair Manual, 5 Spd. Automatic
Transmission 01V, Repair Group 01
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Vehicle speed signal, checking


Required special tools and test equipment

VAG1551 or VAG1552 Scan Tool (ST) with
VAG1551/3 adapter cable
Multimeter US1119 (Fluke 83 or equivalent)
VW1594 connector test kit
Wiring diagrams

Test conditions
Vehicle Speed Sensor (VSS) OK; checking:

Repair Manual, Electrical Equipment, Repair
Group 90


Notes:

To check Vehicle Speed Sensor -G68-, the
vehicle must be driven. A second technician is
required to operate the scan tool during the
road test.
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Continuation
If no speed was indicated:

Notes:
If the LED does not blink:
If the wiring is OK and the LED does not blink:
Repair Manual, Electrical Equipment, Repair Group 90
- Connect VAG1598/22 test box to ECM harness connector page 01
-
67
.
- Connect VAG1527B LED voltage tester between ECM/test box sockets
3 (B+) and 20 (signal).
- Lift vehicle at left-front until wheel is free.
- Switch ignition on and rotate left-front wheel by hand.
LED must blink (very brief blink)
The right-front wheel must not rotate; block it if necessary.For LEDs with little voltage consumption, the LED lights up at half
strength when the ignition is switched on.
- Check wiring from ECM connector, terminal 20 to instrument cluster for
open circuit or short circuit Electrical Wiring Diagrams,
Troubleshooting & Component Locations binder.
-
Check readiness code page 01
-70
. If Diagnostic Trouble Code
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CAN-Bus, checking

When a CAN-Bus malfunction is indicated during
a check of DTC memory of the Engine Control
Module (ECM), refer to the following test to
eliminate the malfunction.

Note:

The information exchange occurs between the
Engine Control Module (ECM) and the
Transmission Control Module (TCM) via a CAN-
Bus.
All signals are carried by 2 wires between the
ECM and the TCM.

Required special tools and test equipment
VAG1551 or VAG1552 Scan Tool (ST) with
VAG1551/3 adapter cable
VAG1598/22 test box
VW1594 connector test kit
Wiring diagrams
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Checking

- Check DTC memory of Transmission Control
Module (TCM).
Repair Manual, 5 Spd. Automatic
Transmission 01V, Repair Group 01 If a DTC regarding the CAN-Bus wire is also
stored in the TCM:

- Switch ignition off.

Electrical Wiring Diagrams, Troubleshooting & Component Locations
binder
If wiring is OK: - Connect VAG1598/22 test box to ECM harness connector page 01
-
67
.
- Check wires from terminal 29 and terminal 41 of test box to
transmission control module for open or short circuit per wiring
diagram. - Replace Transmission Control Module (TCM) and Engine Control
Module (ECM) as necessary and in sequence.
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Test requirements

ECM coding OK page 01
-14


Test sequence

- Switch ignition off.

- Connect VAG1598/22 test box to ECM harness
connector page 01
-67
.

Electrical Wiring Diagrams, Troubleshooting & Component Locations
binder
If the wiring is OK:
If the malfunction occurs again after the ABS control module has been
replaced: - Check signal wiring between ECM/test box terminal 45 and ABS
control module for short circuit or open circuit. - Replace ABS control module.
- Replace Motronic ECM -J220- page 01
-68
.
- Carry out adaptation of throttle valve control module to ECM page
24
-150
.
-
Check readiness code page 01
-70
. If Diagnostic Trouble Code
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- Conduct a test drive ( Safety precautions
page 24
-9 ).

- Check DTC memory of ECM page 01
-16
.
If only the DTC "Fuel level too low" (SAE P1250 /
VAG 17658) is stored in the DTC memory.

Electrical Wiring Diagrams, Troubleshooting & Component Locations
binder - Connect VAG1598/22 test box to ECM harness connector page 01
-
67
.
- Check wire from terminal 21 of test box to instrument cluster for open
circuit or short circuit per wiring diagram.
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