OBD-II code · Network
U0189 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.
Is it safe to drive with U0189?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyAuxiliary heater unpowered
- Less likelyGateway module routing CAN messages incorrectly
- Less likelyCAN terminating resistor (120 Ω) drifted out of spec
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
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.5–3 h
- Emissions test
- Usually unaffected
- Parts involved
- Auxiliary Heater, Can Bus Wiring
Related codes
- U0166Lost Communication with Auxiliary Heater Control Module
- U0186Lost Communication with Audio Amplifier
- U0187Lost Communication with Disc Player Module
- U0188Lost Communication with Audio Rear Control Module
- U018ALost Communication With Headlamp Leveling Control Module B
- U0190Lost Communication with Subwoofer Amplifier Module
- U0191Lost Communication with Television Tuner Module
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.