The Mute Function Not Working

The MUTE Function Not Working:

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

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

Check the 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.