U0166
NetworkModule Communicationlow severityLost Communication with Auxiliary HVAC Control Module
What U0166 Means
Cannot communicate with auxiliary heater or auxiliary climate module.
Symptoms
- Auxiliary heater not working
- Pre-conditioning not available
- Remote start climate control disabled
Common Causes
- Auxiliary HVAC module failure
- CAN bus wiring
- Module power loss
- Fuse blown
Diagnostic Steps
- Check auxiliary HVAC fuse
- Test power and ground
- Check CAN wiring
- Test auxiliary heater element
Where to start: Check fuses for auxiliary climate system.
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