Mute Function On Incoming Or Outgoing phone Call Does Not Work

Mute Function On Incoming Or Outgoing Telephone Call Does Not Work. Incoming Telephone Sound Is Not Relayed Through The Speakers

Fault symptoms
Mute function on incoming and outgoing telephone calls does not work.
Incoming sound is not relayed through the speakers.

Diagnostic help
Applies to handsfree units with mute function and/or line output.

Check wiring harness
Jiggle the wiring harness at several points and in different directions to reveal intermittent breaks and short-circuits in the leads. Observe the multimeter, test lamp or diagnostic instrument during the test.





Diagnostic Procedure

1 Checking the leads between the 10-pin connector and main unit.
- Remove the main unit.
- Take a resistance reading across the 10-pin female connector and the main units 26-pin female connector on the following pins:

Pin, 10-pin Pin, 26-pin
5 6
7 23
8 22

The resistances should be <1 ohm.
- Take a resistance reading across the pin concerned and a good grounding point.
The resistance should be infinite.

Test results OK?
YES
Continue with point 2. The fault does not lie with the car wiring.
NO
Repair or replace lead concerned.
Continue with point 3, Final Check.






2 Checking the handsfree unit
- Check the handsfree unit and leads as described by the supplier of the handsfree unit.

Test results OK?
YES
Continue with Fault diagnosis, general, "Before changing a control module, (65)."
NO
Repair or replace the handsfree unit. Continue with point 3, Final Check.






3 Final check
- Carry out a function check.
- Evaluate the function check.
- Check that the symptom has not recurred.

Has the symptom recurred?
YES
Continue with Fault diagnosis, general, "Before changing a control module, (65)."
NO
The steps taken to rectify the fault were correct.