Signal Missing

Signal missing

Checking the wiring








- Ignition off
- Disconnect connectors D and C from the central electronic module (CEM).
The diagnostic trouble code (DTC) indicates that the communication between the light switch module (LSM), central electronic module (CEM) and combustion preheater module (CPM) is not working. This may be due to a fault in the signal cable between the control modules or a damaged communication device in one or all of the control modules.
Check the signal cable. Check for a short-circuit to supply voltage. Check for a short-circuit to ground.
Take readings between:
- Central electronic module (CEM) terminal #D41 (#41) and light switch module (LSM) terminal #3
- Central electronic module (CEM) terminal #C32 (#32) and combustion preheater module (CPM) terminal #6.
Remedy as necessary.

Other information
- Connecting the breakout box Connecting the Breakout Box, Central Electronic Module (CEM)
- Signal specification Signal Specification
- Location of components Component Location, Central Electronic Module (CEM)
- Switches lights, replacing Service and Repair
- Control module engine coolant heater, replacing Service and Repair
- Checking wiring and terminals Checking Wiring and Terminals

Was a fault detected?

Yes - Verification

No - Replacing the control module

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Replacing the control module
Try a new light switch module (LSM) and combustion preheater module (CPM).
Only replace one control module at a time. Check the function of each control module between each replacement.
Remedy as necessary.

Other information
- Switches lights, replacing Service and Repair
- Control module engine coolant heater, replacing Service and Repair

Continue - Verification

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Verification




Verification

Hint: After carrying out the repair, check that the fault has been remedied.








- Ignition off
- Reinstall the connectors, components etc.
- Ignition on.
Switch between parking lamps and low beam on the light switch module (LSM).
Check on the light switch module (LSM) that each lamp activates correctly.
Activate the combustion preheater module (CPM).
Check that the engine coolant heater is activated.

Are both the light switch module (LSM) and combustion preheater module (CPM) working?

Yes - Troubleshooting procedure complete

No - Fault-tracing information

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Fault-tracing information




Information

Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.

Do you want to exit fault-tracing?

Yes - Exit Fault-tracing

No - Attempt New Test

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Attempt New Test - Checking the wiring

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