Lost Communication with Auxiliary HVAC Control Module
The Auxiliary HVAC Control Module has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. Rear or auxiliary climate control stops working. Typical causes are loss of power or ground at the module, an open or shorted CAN/LIN bus wire, a connector fault, or an internal module failure.
Affected components
- Hvac control module
- Can bus wiring
Common causes
- High likelihood: Auxiliary HVAC module unpowered
- Medium likelihood: CAN wiring to auxiliary HVAC broken
- Low likelihood: Gateway module routing CAN messages incorrectly
Possible symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.