What it means
The turbocharger/supercharger bypass valve A reports a position sensor circuit low condition. Boost recirculation cannot be commanded reliably.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The position sensor on turbocharger or supercharger bypass valve A tells the control module how far the boost-recirculation valve has moved. This code sets when the sensor signal is abnormally low, which can happen if the signal wire is shorted to ground or the sensor is internally shorted.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light on
- Significant power loss / limp mode
- Possible blue or black smoke from exhaust
- Whistling or hissing sound from intake
How to diagnose it
- Save freeze-frame data and compare commanded bypass valve A position with live sensor feedback, if available; a persistently low or implausible signal helps narrow the fault.
- Inspect valve A and its connector for corrosion, loose pins, or heat-damaged or chafed wiring.
- Check the position-sensor harness for a signal wire pinched against ground or damaged near the valve and intake plumbing.
- Using the wiring diagram, test the valve A sensor signal for a short to ground and check its supply and ground connections.
- If the wiring and connector are sound, test the valve A position sensor against the manufacturer's procedure and replace it if it is internally shorted.
Common fixes
- Clean or repair corroded valve A sensor connector terminals.
- Repair the position-sensor signal wire where it is shorted to ground.
- Repair damaged sensor supply or ground wiring.
- Replace the bypass valve A position sensor or valve assembly if testing confirms an internal fault.
Can I keep driving?
Avoid hard acceleration, towing, and high-speed driving if power is reduced or the vehicle enters limp mode. The valve position feedback is unreliable, which can impair boost control and worsen drivability.
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.