OBD-II code · Network
U0657 Lost Communication With Turbocharger/Supercharger Bypass Valve A Position Sensor
The vehicle bus reports loss of communication with smart turbocharger bypass valve A position sensor (compressor recirculation/blow-off valve position). Closed-loop control loses its actual feedback.
Is it safe to drive with U0657?
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
- Turbo Bypass Valve A Position Sensor, Vehicle Bus Wiring
Related codes
- U066BLost Communication With Turbocharger/Supercharger Bypass Valve B Position Sensor
- U0654Lost Communication With Diesel Intake Air Flow A Position Sensor
- U0655Lost Communication With Diesel Intake Air Flow B Position Sensor
- U0656Lost Communication With Turbocharger/Supercharger Boost Control A Position Sensor
- U0658Lost Communication With Windshield Temperature Sensor
- U0659Lost Communication With Left Front Temperature Actuator
- U065ALost Communication With Right Front Temperature Actuator
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.