OBD-II code · Network
U063C Lost Communication With Coolant Bypass Valve Actuator B
The vehicle bus reports loss of communication with smart coolant bypass valve actuator B. Coolant routing for thermal management cannot be commanded.
Is it safe to drive with U063C?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyBus wiring open or shorted
- PossibleModule without power or ground
- PossibleModule failed
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
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Coolant Bypass Valve Actuator B, Vehicle Bus Wiring
Related codes
- U063BLost Communication With Coolant Bypass Valve Actuator A
- U0639Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor B
- U063ALost Communication With Hybrid/EV Electronics Coolant Temperature Sensor C
- U063DLost Communication With Hybrid/EV Electronics Coolant Pump A
- U063ELost Communication With Exhaust Heat Exchanger Bypass Valve Actuator A
- U063FLost Communication With Engine Coolant Flow Control Valve Position Sensor
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.