Test F: Loud Popping Sound When Cycling The Ignition Switch

PINPOINT TEST F: LOUD POPPING SOUND WHEN CYCLING THE IGNITION SWITCH

Normal Operation
Voltage is sent through the start input circuit CBP13 (GY/BN) to the audio control module (ACM) with the key in START. Upon receiving this signal, the ACM mutes all speaker outputs to eliminate the possibility of speaker pops during engine cranking.

For the Audiophile audio system, the ACM disables the subwoofer while the key is in START by keeping the enable signal below 0.4 volts on circuit SME23 (VT/RD).

For the THX(R) audio system, the ACM disables the audio digital signal processing (DSP) module while the key is in START by keeping the enable signal below 0.4 volts on circuit SME23 (VT/RD).

This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Subwoofer amplifier (Audiophile)
- DSP module (THX(R) audio system)
- ACM

F1:

F1-F4: