Test I: Loud Popping Sound When Cycling The Ignition

PINPOINT TEST I: LOUD POPPING SOUND WHEN CYCLING THE IGNITION

Normal Operation
Voltage is sent through the start input circuit CBP28 (GY/VT) 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.

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.

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

I1:

I1-I4: