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

NO RESPONSE FROM HVAC (A/C HEATER CONTROL)

For a complete wiring diagram, Refer to the Wiring Information Electrical Diagrams.






1. TEST FOR INTERMITTENT CONDITION
1. Turn the ignition on.

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

2. With the scan tool, select ECU view.

NOTE: A red X will be next to the module that is not communicating, indicating that the module is not active on the Bus network. A green check indicates that the module is active on the Bus network.

Does the scan tool display a red X next to the module?

Yes

- Go To 2

No

- The no response condition is not present at this time. Using the wiring diagram/schematic as a guide, inspect the wiring for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals.

2. FUSED B(+) CIRCUITS OPEN OR SHORTED
1. Turn the ignition off.
2. Using the wiring diagram as a guide, disconnect the appropriate wiring harness connectors.
3. Using a 12-volt test light connected to ground, check the Fused B(+) circuits.

Does the test light illuminate brightly for each circuit?

Yes

- Go To 3

No

- Repair the Fused B(+) circuits for an open or short.
- Perform the BODY VERIFICATION TEST Verification Tests.

3. FUSED RUN RELAY OUTPUT CIRCUITS OPEN OR SHORTED
1. Turn the ignition on.
2. Using a 12-volt test light connected to ground, check the Fused Run Relay Output circuits.

Does the test light illuminate brightly for each circuit?

Yes

- Go To 4

No

- Repair the Fused Run Relay Output circuits for an open or short.
- Perform the BODY VERIFICATION TEST Verification Tests.

4. GROUND CIRCUITS OPEN
1. Turn the ignition off.
2. Using a 12-volt test light connected to 12-volts, check each ground circuit.

Does the test light illuminate brightly for each circuit?

Yes

- Go To 5

No

- Repair the ground circuit for an open.
- Perform the BODY VERIFICATION TEST Verification Tests.

5. CAN B BUS CIRCUITS OPEN

NOTE: One open circuit will not cause this condition.

1. Measure the voltage between the all the CAN B Bus (-) circuits and ground.
2. Measure the voltage between the all the CAN B Bus (+) circuits and ground.

Is there any voltage present on either circuit?

Yes

- Replace the A/C Heater Control.
- Perform the BODY VERIFICATION TEST Verification Tests.

No

- Inspect the connector for damage. Repair the CAN B Bus circuits for an open.
- Perform the BODY VERIFICATION TEST Verification Tests.