1996 AUDI A4 ignition

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Display on VAS5051:
- Determining via road test whether vehicle speed is displayed in display
field -3-.
- If vehicle speed is not display, lift vehicle -if possible using a vehicle lift-
until front left wheel is free.
- 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).
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Data transfer between Engine Control
Module (ECM) and CAN-bus capable
control modules, checking


Notes:

Data exchange between individual control
modules occurs via a bus system.
The term "CAN-bus" refers to a system that
transports and distributes data.
The wire connections between the control
modules, via which data is transferred, are
referred to as data wires.
Data is transferred to the connected control
modules serially (one after the other) via these
data wires (i.e. engine speed, accelerator
position).

Checking bus system
The DTC table suggested checking the data
exchange between the Engine Control Module
(ECM) and CAN capable control modules.

- Connect VAS5051 tester Page 01
-7 and
select vehicle system "01 - Engine electronics".
Ignition must remain switched on for this.
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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 the control modules connected across the bus wires and
check the bus wires for an open circuit. - Replace control module 1 if no malfunctions can be found in the bus
wires.
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Example 2:
From the DTCs stored in the memories, you have determined that control
module 2 is not communicating with control modules 1 and 3.
Electrical Wiring Diagrams, Troubleshooting & Component Locations Control module
DTCs stored in DTC memories:
1
Missing signal from control module 2
2 Missing signal from control module 1Missing signal from control module 3
3 Missing signal from control module 2
- Switch ignition off.
- Disconnect the control modules connected across the bus wires and
check the bus wires for an open circuit. - Replace control module 2 if no malfunctions can be found in the bus
wires.
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Example 3:
Using the DTCs stored in the memories, you
have determined that none of the control
modules are sending or receiving signals.

Control
module
DTCs stored in DTC
memories:
1
Powertrain CAN-bus faulty
2 Powertrain CAN-bus faulty
3 Powertrain CAN-bus faulty

- Switch ignition off.

Electrical Wiring Diagrams, Troubleshooting & Component Locations - Disconnect the control modules connected across the bus wires and
check bus wires for a short circuit to B+ and Ground (GND).
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If you cannot determine a cause for the DTC
"Powertrain CAN-bus malfunction, check
whether the DTC is caused by one of the
control modules.
All control modules that use the CAN-bus are still
disconnected. Ignition is switched off.

- Connect one of the control modules.

- Connect VAG 1551 scan tool. Switch ignition on,
and erase the DTC memory of the control
module you just connected. End scan tool output
using the "End Output" function 06.

- Switch ignition off and on again.

- Leave ignition on for 10 seconds. Then, read the
DTC memory of the control module you just
connected.

- If the DTC "Powertrain CAN-bus malfunction" is
displayed, replace the control module you just
connected.

- If the DTC "Powertrain CAN-bus malfunction" is
not displayed, connect the next control module
and repeat the procedure.
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