P0239
Turbocharger/Supercharger Boost Sensor B Circuit
Turbo / boost control
Generic OBD-II
High
What it means
P0239 means the ECM has detected a fault in the "B" turbocharger or supercharger boost pressure sensor circuit. This sensor tells the ECM how much boost the engine is making, so an unreliable signal usually makes the ECM cut boost or enter limp mode to stay safe. It is an electrical/sensor fault — despite some databases flagging it as a misfire, it does not directly cause misfires.
High
Can I keep driving? Driveable but likely with reduced power — the ECM often limits boost or drops into limp mode when it can't read boost pressure reliably.
Common symptoms
What you'll notice
- Check-engine light on
- Reduced power or limp mode
- Hesitation or surging under acceleration
- Poor fuel economy
Common causes
Most likely first
- Faulty boost pressure sensor 'B'Likely
- Open or shorted signal wiring to the sensorCommon
- Corroded or loose sensor connectorCommon
- Damaged 5V reference or ground circuitLess often
- Faulty ECM (least likely)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and inspect the boost sensor 'B' connector and any pressure hose feeding it.
- Check the sensor's reference voltage and ground against spec.
- Backprobe the signal wire and compare the reading to a known-good value or scan-tool PID.
- Replace the boost pressure sensor if it reads out of range with good wiring.
- Repair damaged wiring or connectors if the sensor tests good. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0239?+
Short-term, yes, but expect reduced power. The ECM limits boost to protect the engine, so have it diagnosed before hard driving or towing.
Can I just clear P0239?+
It returns once the ECM sees the faulty circuit again. The sensor or its wiring must be repaired first.
Related codes
Often seen with P0239
Read & clear P0239 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX