Checking Hands-Free and Handset Mode, Phone Module (PHM)

Checking hands-free and handset mode

Fault-tracing information




The phone module (PHM) determines whether the call should be connected via hands-free or the handset based on the hook signal of the handset. If the handset is in its holder (i.e. "on the hook"), all calls are connected via hands-free. The handset is activated when it is removed from its holder.
Check that the handset is properly positioned in its holder.
- Ignition in position 1.
- Telephone call connected.
Switch between handset and hands-free mode via the menu in the display.

Do both handset and hands-free mode work?

Yes - Verification

No - Checking the telephone holder magnet

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Checking the telephone holder magnet
The handset houses a detector that is actuated by the magnetic field from the telephone holder magnet. It closes or opens a circuit depending on whether the handset is in or out of the holder.
Check the hook signals by connecting adapter cable 951 1463 Adapter 22-16-14 pin 951 1463 Adapter 22-16-14 Pin and measuring box 951 1428 Breakout box 951 1428 Breakout Box to the phone module.
Handset on: U = 1.9 V.
Handset off: U = 3.34 V.
Open circuit: U = 5 V.
If the correct voltage level value is not obtained when the handset is hung up, check the magnet as follows:
- Lift up the handset.
- Run a metal object over the magnet (paper clip or similar). See the illustration.
- If there is a strong reaction, the magnet is functional.
- If there is no reaction, replace the holder with magnet.
If the function check is successful the fault has been remedied.

Other information:
- Microphone telephone Service and Repair
- Signal specification Signal Description, Phone Module (PHM)





Was a fault detected?

Yes - Verification

No - Checking the connectors

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Checking the connectors
With functioning magnet but still lost function of the handset, try checking the connectors for the handset.
- Check that the connector (1) for the secrecy handset in the center console is connected.
- Check that the cable terminals of the connector have not retracted and that they are in the locked position.
With correctly connected connector but still lost function of the handset, try with another handset.
If this handset works, replace with a new handset.
If there is no function, replace the holder with magnet.

Other information:
- Telephone handset Telephone Handset





Was a fault detected?

Yes - Verification

No - No Fault Found

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Verification









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

- Ignition off.
- Reinstall the connectors, components etc.
- Ignition on.
- Switch on the carphone.
Make a call so that both the handset and the hands-free system are used. See the instruction manual.

Is the carphone working?

Yes - Troubleshooting procedure complete

No - Remedy as necessary

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