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Three or more control modules are
communicating across a "two-line bus
system".
- Analyze the DTCs stored in the memories of the
control modules.
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
Hardware malfunctioning
2 Hardware malfunctioning
3 Hardware malfunctioning
- Switch ignition off.
Electrical Wiring Diagrams, Troubleshooting & Component Locations - Disconnect the control modules connected across the bus wires and
check for a short circuit between the bus wires.
- Check the bus wires for short circuit to B+ or Ground (GND).
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- If you cannot determine a cause for the DTC
"Hardware malfunction", check whether the DTC
is caused by one of the control modules.
All control modules that use the CAN-bus are
still disconnected. The ignition is switched off.
- Connect one of the control modules.
- Connect the VAG1551 Scant Tool (ST) or the
VAG1552 mobile 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 then on.
- Leave ignition on for 10 seconds. Then, read
the DTC memory of the control module you
just connected.
- If the DTC "Hardware malfunction" is
displayed, replace the control module you just
connected.
- If the DTC "Hardware malfunction" is not
displayed, connect the next control module
and repeat the procedure.
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