What it means
The vehicle bus reports loss of communication with the boost control B position sensor. Closed-loop control of the wastegate/VTG actuator on this turbo loses its actual feedback signal.
At a glance
- Usually lights the warning light of the system that lost communication
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The boost control B position sensor reports the actual position of turbo B's wastegate or variable-geometry actuator for closed-loop control. The engine controller monitors messages from this sensor; U02B0 sets when they stop arriving, so commanded actuator movement cannot be checked against actual position.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module 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
How to diagnose it
- Scan all modules for network and boost-control faults, and review freeze-frame data to see when the B position feedback disappeared.
- Check live data for boost control B position sensor communication, commanded position, and reported position, if available.
- Inspect the B position sensor connector and nearby bus wiring for looseness, corrosion, chafing, or heat damage.
- Check the sensor or its module's power and ground circuits under the conditions specified by the manufacturer.
- Test the network wiring to the B position sensor for an open, short, or poor connection using the manufacturer's procedure.
- If wiring, power, and ground are sound, follow the manufacturer's tests to confirm whether the B position sensor or its module has failed.
Common fixes
- Reconnect or clean the boost control B position sensor connector.
- Repair damaged communication wiring to the B position sensor.
- Restore the sensor or module's power or ground supply.
- Replace the B position sensor or its module if testing confirms it has failed.
Can I keep driving?
The engine may limit boost or enter limp mode because it cannot verify turbo B actuator position. Avoid hard acceleration and towing; stop safely if power loss makes driving unsafe or other engine warnings appear.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.