What it means
Position sensor A signal voltage below the lower limit — short to ground in the signal line or open reference voltage at the sensor.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Turbocharger boost control position sensor A reports wastegate or variable-geometry actuator position to the engine control module. This code sets when the sensor A signal falls below its expected range, often because the signal is grounded or the sensor has lost its reference supply.
Common causes
Most likely first.
- Signal wire shorted to ground
- Missing 5 V reference at the sensor
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Reduced engine power or acceleration
- Poor boost response
How to diagnose it
- Record freeze-frame data and check sensor A live feedback to confirm that the position reading is at or near its lowest value.
- With the engine off and cool, inspect sensor A wiring and connector near the turbo for chafing, heat damage, corrosion, or pushed-back pins.
- Check whether the sensor has its specified reference supply and a sound ground using the manufacturer's specification.
- Test the sensor A signal wire for a short to ground or an open circuit, and inspect the reference circuit for an interruption.
- If the wiring and supplies pass, test sensor A output while the actuator moves according to the manufacturer's procedure.
Common fixes
- Repair a signal wire shorted to ground or damaged near the turbo.
- Restore a missing reference supply by repairing the affected wire or connector.
- Clean or repair corroded, loose, or pushed-back sensor A connector terminals.
- Replace sensor A or its actuator assembly if the signal remains low with correct wiring and supply.
Can I keep driving?
Reduced power and poor boost response may make merging or passing difficult, so avoid high-load driving and towing. Stop in a safe place if the loss of power prevents you from driving safely.
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.