Pinpoint Test E: Loud Popping Sound When Cycling The Ignition

Information and Entertainment System

Pinpoint Test E: Loud Popping Sound When Cycling The Ignition

Refer to Wiring Diagram Set 130, Audio System/Navigation for schematic and connector information Electrical Diagrams.

Normal Operation

Voltage is sent from the Smart Junction Box (SJB) to the Audio Front Control Module (ACM) through the start input circuit when the ignition is in the START position. Upon receiving this signal, the ACM (Audio Front Control Module) mutes all speaker outputs to eliminate the possibility of voltage spikes producing a popping noise through the speakers.

For the Premium sound system, the ACM (Audio Front Control Module) disables the subwoofer while the ignition is in the START position by keeping the enable signal below 0.4 volt. If there is a short to voltage on the input circuit, distortion is heard in the subwoofer whenever the ACM (Audio Front Control Module) is powered up, and that should be the primary concern addressed. If the subwoofer has distorted sound, GO to Pinpoint Test D Pinpoint Test D: The Subwoofer Is Inoperative/Does Not Operate Correctly.

This pinpoint test is intended to diagnose the following:

- Fuse

- Wiring, terminals or connectors

- Subwoofer (Premium sound)

- ACM (Audio Front Control Module)

PINPOINT TEST E : LOUD POPPING SOUND WHEN CYCLING THE IGNITION

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

E1 CHECK THE INPUT CIRCUIT FOR VOLTAGE

- Ignition OFF.

- Disconnect: ACM (Audio Front Control Module) C240A.

- Disconnect: Starter Relay.

- Hold the key in the START position.

- Measure the voltage between the ACM (Audio Front Control Module) C240A-15, circuit CBP28 (GY/VT), harness side and ground.





Is the voltage greater than 10 volts?

Yes
For the Premium sound system, GO to E2.

For all others, INSTALL a new ACM (Audio Front Control Module). REFER to Audio Control Module (ACM) . TEST the system for normal operation.

No
VERIFY the SJB (Smart Junction Box) fuse 28 (5A) is OK. If OK, REPAIR the circuit. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams.

E2 ISOLATE THE SUBWOOFER

- Ignition OFF.

- Connect: ACM (Audio Front Control Module) C240A.

- Disconnect: Subwoofer C466.

- Cycle the key through all of the ignition switch positions.

Is a loud popping sound present?

Yes
INSTALL a new ACM (Audio Front Control Module). REFER to Audio Control Module (ACM) . TEST the system for normal operation.

No
INSTALL a new subwoofer. REFER to Speaker - Subwoofer . TEST the system for normal operation.