Pinpoint Test J: Loud Popping Sound When Cycling The Ignition

Information and Entertainment System

Pinpoint Tests

Pinpoint Test J: Loud Popping Sound When Cycling The Ignition

Refer to Wiring Diagram Set 130, Audio System/Navigation for schematic and connector information. 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 mutes all speaker outputs to eliminate the possibility of voltage spikes producing a popping noise through the speakers.

For the Audiophile audio system, the ACM disables the subwoofer and the audio amplifier while the ignition is in the START position by keeping the enable circuit voltages below 0.4 volt.

If there is a short to voltage on either of the enable circuits, distortion is heard in the speakers whenever the ACM 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



PINPOINT TEST J: 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.

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J1 CHECK THE START INPUT CIRCUIT VOLTAGE


- Ignition OFF.
- Disconnect: ACM C290a.
- Disconnect: Starter Relay.
- Hold the key in the START position.
- Measure the voltage between the ACM C290a-15, circuit CBP11 (BN), harness side and ground.




- Is the voltage greater than 10 volts?

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

No
VERIFY the Smart Junction Box (SJB) fuse 11 (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.

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