Lost Communication With HVAC Control Module

9029-LOST COMMUNICATION WITH HVAC CONTROL MODULE

For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
With the ignition on.

Battery voltage between 10 and 16 volts.

IOD fuse installed.

EIS (CGW) is configured correctly.

- Set Condition:
Bus messages not received from the A/C Control Module (HVAC) for approximately 2 to 5 seconds.





Diagnostic Test

1. VERIFY DTC IS ACTIVE
NOTE: Ensure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding.

With the scan tool, read active DTCs.
Is this DTC active?

Yes

- Go To 2

No

- Refer to the Stored Lost Communication test procedure. Stored Lost Communication DTCs

2. CHECK FOR ANY OF THE FOLLOWING ACTIVE DTCS
With the scan tool, read active DTCs from all modules.

NOTE: Check for EIS (CGW) configuration, CAN C hardware electrical, VIN Missing/Mismatch, battery or ignition related DTCs.

Does the scan tool display any active DTCs to the conditions listed above?

Yes

- Diagnose and repair the DTC.

No

- Go To 3

3. VERIFY THAT THE HVAC IS ACTIVE ON THE BUS
Turn the ignition on.
With the scan tool, select Network Diagnostics.
Verify that the HVAC is active on the bus.
Is the HVAC active on the bus?

Yes

- Go To 4

No

- Refer to the No Response test procedure.
Communications - Verbose Codes

4. CHECK FOR ADDITIONAL COMMUNICATION RELATED DTCS
With the scan tool, select Network Diagnostics.
Is there more than one module with active DTCs "Logged Against" the HVAC?

Yes

- Replace/update the A/C Control Module (HVAC).
- Perform the BODY VERIFICATION TEST - VER 1.Body Verification Test.

No

- Replace/update the module that set this DTC.
- Perform the appropriate VERIFICATION TEST. Verification Tests