No Response From HVAC (A/C Heater Control Module)

NO RESPONSE FROM HVAC (A/C HEATER CONTROL MODULE)

For a complete wiring diagram, refer to the Wiring Information.





Diagnostic Test

1. TEST FOR INTERMITTENT CONDITION

NOTE: Check for any TSB(s) related to the condition. If a TSB applies, perform the procedure outlined in the TSB before continuing.

1. Turn the ignition on.

NOTE: Make sure the IOD fuse is installed and battery voltage is between 10.0 and 16.0 volts.

2. With the scan tool, read the module status.

NOTE: Check the BCM for any active CAN hardware DTCs, perform DTC before proceeding.

Does the scan tool indicate that the module is active on the bus?

Yes

- The no response condition is not present at this time. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.

No

- Go To 2

2. CHECK THE FUSED B(+) CIRCUIT FOR AN OPEN OR SHORT




1. Turn the ignition off.
2. Disconnect the A/C Heater Control harness connector.
3. Using a 12-volt test light connected to ground, check the Fused B(+) circuit.

Does the test light illuminate brightly?

Yes

- Go To 3

No

- Repair the open or short in the Fused B(+) circuit.
- Perform the BODY VERIFICATION TEST. Body Verification Test .

3. CHECK THE GROUND CIRCUIT FOR AN OPEN




1. Using a 12-volt test light connected to 12-volts, check the Ground circuit.

Does the test light illuminate brightly?

Yes

- Go To 4

No

- Repair the open in the Ground circuit.
- Perform the BODY VERIFICATION TEST. Body Verification Test .

4. CHECK THE FUSED RUN RELAY OUTPUT CIRCUIT FOR AN OPEN OR SHORT




1. Turn the ignition on.
2. Using a 12-volt test light connected to ground, check the (F921) Fused Run Relay Output circuit.

Does the test light illuminate brightly?

Yes

- Go To 5

No

- Repair the open or short in the Fused Run Relay Output circuit.
- Perform the BODY VERIFICATION TEST. Body Verification Test .

5. CHECK THE CAN INTERIOR BUS (125K) CIRCUITS FOR AN OPEN




1. Measure the resistance of the (D264) CAN Interior Bus (125K) (-) circuit between the BCM harness connector and the A/C Heater Control harness connector.
2. Measure the resistance of the (D265) CAN Interior Bus (125K) (+) circuit between the BCM harness connector and the A/C Heater Control harness connector.

Are the resistances below 5.0 Ohms?

Yes

- Replace the A/C Heater Control Module. A/C And Heater Control - Removal.
- Perform the BODY VERIFICATION TEST. Body Verification Test .

No

- Repair the open in the CAN Interior Bus (125K) circuit.
- Perform the BODY VERIFICATION TEST. Body Verification Test .