U0657 code meaning
Lost Communication With Turbocharger/Supercharger Bypass Valve A Position Sensor
Network system Generic code U06xx codes Check engine light
What U0657 means
The bypass valve meant here sits on the intake side: on turbocharged gasoline engines it lets compressed air recirculate when the throttle shuts, and on supercharged engines it routes air around the blower at light load. When the valve is electrically driven and reports its position digitally, U0657 marks that the position data from valve A has stopped arriving. No manufacturer publishes a description of U0657, so the exact valve and its protocol come from the vehicle's own service information. Analog circuit faults of the same sensor are P2BBB to P2BBD and an adaptation problem is P2BBE; valve B has U066B. Without position feedback the controller cannot tell whether surplus air is being released, so it may restrict boost to protect the compressor.
U0657 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0657
- MIL on
- Less boost or hesitant throttle response
- Unusual whoosh or flutter when lifting off
Common causes of U0657
- Most likelyWiring to the bypass valve open, shorted or chafed
- PossibleLoose or corroded valve connector
- PossiblePosition sensor in the valve failed
- Less likelyEngine controller input fault
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Turbo bypass valve a position sensorVehicle bus wiring
What each part of U0657 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 57 | The exact fault in that area. |
What to do next
- Note U0657 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0657
What does U0657 mean?
U0657 means "Lost Communication With Turbocharger/Supercharger Bypass Valve A Position Sensor". The bypass valve meant here sits on the intake side: on turbocharged gasoline engines it lets compressed air recirculate when the throttle shuts, and on supercharged engines it routes air around the blower at light load. It is a generic code, so it means the same on every make.
Is it safe to drive with U0657?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will U0657 fail an emissions test?
Yes, it can. U0657 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U0657 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will U0657 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.