Pinpoint Test I: The Audio Control Module (ACM) Does Not Respond To The Scan Tool

Communications Network

Pinpoint Tests

Pinpoint Test I: The Audio Control Module (ACM) Does Not Respond To The Scan Tool

Refer to Wiring Diagram Set 14, Module Communications Network for schematic and connector information. Diagrams By Number

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

Normal Operation

The Audio Control Module (ACM) communicates with the scan tool through the Medium Speed Controller Area Network (MS-CAN). Circuits VDB06 (GY/OG) (HS-CAN +) and VDB07 (VT/OG) (HS-CAN -) provide the network connection to the ACM. The ACM shares the MS-CAN with the HVAC module, the Accessory Protocol Interface Module (APIM), the Smart Junction Box (SJB), the Driver Seat Module (DSM), the Rear Entertainment Module (RETM), the Satellite Digital Audio Receiver System (SDARS) module, the Liftgate/Trunk Module (LTM) and the Instrument Cluster (IC). Voltage for the ACM is provided by circuit SPB39 (WH/RD) and circuit GD103 (BK/BU) provides ground.

This pinpoint test is intended to diagnose the following:

- Fuse
- Wiring, terminals or connectors
- ACM



PINPOINT TEST I: THE ACM DOES NOT RESPOND TO THE SCAN TOOL

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

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I1 CHECK THE ACM VOLTAGE SUPPLY CIRCUITS FOR AN OPEN


- Ignition OFF.
- Disconnect: ACM C240a.
- Ignition ON.
- Measure the voltage between the ACM C240a-1, circuit SPB39 (WH/RD), harness side and ground.




- Is the voltage greater than 10 volts?

Yes
GO to I2.

No
VERIFY the SJB fuse 39 (20A) is OK. If OK, REPAIR the circuit. If not OK, Refer to the Wiring Diagrams to identify the possible causes of the short circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.

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I2 CHECK THE ACM GROUND CIRCUIT FOR AN OPEN


- Ignition OFF.
- Measure the resistance between the ACM C240a-13, circuit GD103 (BK/BU), harness side and ground.




- Is the resistance less than 5 ohms?

Yes
GO to I3.

No
REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.

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I3 CHECK THE MS-CAN CIRCUITS BETWEEN THE ACM AND THE DATA LINK CONNECTOR (DLC) FOR AN OPEN


- Disconnect: ACM C240c.
- Measure the resistance between the ACM C240c-15, circuit VDB06 (GY/OG), harness side and the DLC C251-3, circuit VDB06 (GY/OG), harness side.




- Measure the resistance between the ACM C240c-16, circuit VDB07 (VT/OG), harness side and the DLC C251-11, circuit VDB07 (VT/OG), harness side.




- Are the resistances less than 5 ohms?

Yes
GO to I4.

No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.

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I4 CHECK FOR CORRECT ACM OPERATION


- Disconnect all of the ACM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all of the ACM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?

Yes
INSTALL a new ACM. CLEAR the DTCs. REPEAT the network test with the scan tool.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the network test with the scan tool.

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