Pinpoint Test S: Loud Popping Sound When Cycling The Ignition Switch

Information and Entertainment System

Pinpoint Test S: Loud Popping Sound When Cycling The Ignition Switch

Refer to Wiring Diagram Set 130, Audio System/Navigation for schematic and connector information. [1][2]Diagrams By Number

Normal Operation

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

For premium sound, the ACM (Audio Control Module) disables the audio amplifier and subwoofer amplifier while the ignition is in the START position by keeping the enable circuit voltages below 0.4 volt.

For the Sony(R) and THX(R) sound systems, the ACM (Audio Control Module) disables the audio Digital Signal Processing (DSP) module while the ignition is in the START position by keeping the enable circuit voltage below 0.4 volt.

If there is a short to voltage on any of the enable circuits, distortion is heard in the speakers whenever the ACM (Audio Control Module) is powered up, and that should be the primary concern addressed. If the speakers have distorted sound, GO to Symptom Chart - Sound Quality. Symptom Chart - Sound Quality

This pinpoint test is intended to diagnose the following:

- Fuse

- Wiring, terminals or connectors

- ACM (Audio Control Module)

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

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

S1 CHECK THE START INPUT CIRCUIT VOLTAGE

- Ignition OFF.

- Disconnect: ACM (Audio Control Module) C240A.

- Disconnect: Starter Relay.

- Hold the key in the START position.

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





Is the voltage greater than 10 volts?

Yes
INSTALL a new ACM (Audio Control Module). REFER to Audio Control Module (ACM) - Fusion or Audio Control Module (ACM) - MKZ . TEST the system for normal operation.

No
VERIFY the Smart Junction Box (SJB) 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. [1][2]Diagrams By Number