Lost Communication with Auxiliary Heater Control Module
The HVAC controller has lost the auxiliary fuel-fired heater module. Pre-heating cannot be commanded; the heater stays inactive.
Affected components
- Auxiliary heater
- Can bus wiring
Common causes
- High likelihood: Auxiliary heater unpowered
- Low likelihood: Gateway module routing CAN messages incorrectly
- Low likelihood: CAN terminating resistor (120 Ω) drifted out of spec
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
Related codes
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.