OBD-II code · Network
U066C Lost Communication With Exhaust Heat Exchanger Bypass Valve Actuator B
The vehicle bus reports loss of communication with smart exhaust heat exchanger bypass valve actuator B. Exhaust-heat recovery cannot be commanded; cabin/coolant warm-up may slow down.
Is it safe to drive with U066C?
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
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Exhaust Heat Exchanger Bypass Actuator B, Vehicle Bus Wiring
Related codes
- U063ELost Communication With Exhaust Heat Exchanger Bypass Valve Actuator A
- U0669Lost Communication With EGR Sensor D
- U066ALost Communication With EGR Sensor E
- U066BLost Communication With Turbocharger/Supercharger Bypass Valve B Position Sensor
- U066DLost Communication With Charge Air Cooler Temperature Sensor Bank 1
- U066ELost Communication With Charge Air Cooler Temperature Sensor Bank 2
- U066FLost Communication With Low Pressure Fuel System Sensor
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.