Pinpoint Test F: The Auxiliary Heater Control Module (AHCM) Does Not Respond To The Scan Tool

Communications Network

Pinpoint Tests

Pinpoint Test F: The Auxiliary Heater Control Module (AHCM) 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 54, Manual Climate Control System for schematic and connector information. Diagrams By Number

Refer to Wiring Diagram Set 55, Automatic Climate Control for schematic and connector information. Diagrams By Number

Normal Operation

The Auxiliary Heater Control Module (AHCM) is optional equipment on diesel engine vehicles only. The AHCM communicates with the scan tool through the High Speed Controller Area Network (HS-CAN).

This pinpoint test is intended to diagnose the following:

- Fuse
- Wiring, terminals or connectors
- AHCM



PINPOINT TEST F: THE AHCM DOES NOT RESPOND TO THE SCAN TOOL

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

NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.

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F1 CHECK THE AHCM VOLTAGE SUPPLY CIRCUIT FOR AN OPEN


- Disconnect: AHCM C2463c.
- Ignition ON.
- Measure the voltage between the AHCM C2463c-1, circuit CBP37 (WH), harness side and ground.




- Is the voltage greater than 10 volts?

Yes
GO to F2.

No
VERIFY the Smart Junction Box (SJB) fuse 37 (10A) is OK. If OK, REPAIR the circuit in question. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. CLEAR the DTCs. REPEAT the network test with the scan tool. Diagrams By Number

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F2 CHECK THE AHCM GROUND CIRCUIT FOR AN OPEN


- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Disconnect: AHCM C2463b.
- Measure the resistance between the AHCM C2463b-1, circuit ZED08 (BK), harness side and ground.




- Is the resistance less than 5 ohms?

Yes
GO to F3.

No
REPAIR the circuit. CONNECT the negative battery cable. CLEAR the DTCs. REPEAT the network test with the scan tool.

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F3 CHECK THE HS-CAN CIRCUITS BETWEEN THE AHCM AND THE DLC FOR AN OPEN


- Measure the resistance between the AHCM C2463c-3, circuit VDB04 (WH/BU), harness side and the Data Link Connector (DLC) C251-6, circuit VDB04 (WH/BU), harness side.




- Measure the resistance between the AHCM C2463c-4, circuit VDB05 (WH), harness side and the DLC C251-14, circuit VDB05 (WH), harness side.




- Are the resistances less than 5 ohms?

Yes
CONNECT the negative battery cable. GO to F4.

No
REPAIR the circuit in question. CONNECT the negative battery cable. CLEAR the DTCs. REPEAT the network test with the scan tool.

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F4 CHECK FOR CORRECT AHCM OPERATION


- Disconnect all the AHCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the AHCM 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 AHCM. 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.

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