Faulty Signal

Faulty signal

Checking fuses and power supply




- Ignition on.
The phone module (PHM) is powered via a fuse from the central electronic module (CEM).
Check whether the fuse for the phone module (PHM) is half burned by testing using a new fuse.

Hint: A half burned fuse can cause intermittent faults.

Check the power supply to the phone module (PHM) by:
- measuring the voltage between phone module (PHM) connector A terminals #5 (#5) and A #6 (#6)
- measure the battery voltage.
The fault is in the power supply cable if the difference between the power supply for the control module and battery voltage is greater than 2.5 V.
There may be an internal fault in the phone module (PHM) if the difference is less than 2.5 V.
Remedy as necessary.

Other information:
- For further information about the fuses and relays, see the Wiring Diagram
- Signal specification Signal Specification, Phone Module (PHM)
- Connecting the breakout box Connecting the Breakout Box, Phone Module (PHM)
- Location of components Location of Components, Phone Module (PHM)
- Phone Module (PHM) Phone Module (PHM)
- Checking wiring and terminals Checking Wiring and Terminals









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
- Activate the carphone.
Make a call so that both the handset and the hands-free system are used. See the instruction manual.
Ignition off.
Ignition on.
Read off the diagnostic trouble codes (DTCs).
Check that the relevant diagnostic trouble code (DTC) has switched status from permanent to intermittent fault.





Has the status of the diagnostic trouble code (DTC) changed?

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 fuses and power supply

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