B1287 04

B1287 01, B1287 02, B1287 04

B1287 01: Mute Amp Control Circuit, Short to B+

B1287 02: Mute Amp Control Circuit, Short to Ground

B1287 04: Mute Amp Control Circuit, Open

Fault symptoms

Mute not functioning.
No sound
No sound from telephone/OnStar.
Interference noise when the radio is switched off or in the mute mode.
Clicks from the speakers when switching off the unit.

Type of diagnosis

Continuous when.

Enable criteria

Ignition ON.
Radio/CD switched on
Battery voltage between 9 and 16V (+/- 1V).
(Pin 6 K14 on the control module must be connected to the amplifier pin 12)

Fault criteria

01 Amplifier mute circuit short circuited to B+.
02 Amplifier mute circuit short circuited to ground.
04 Open circuit in the amplifier mute circuit.

Checking the wiring harness

Jiggle the wiring harness at several points and in different directions to detect intermittent breaks and short circuits. Check switches, connectors and crimp connections for oxidation, withdrawn pins and pin clamping force.

Fault Diagnosis Procedure