O2 Sensor Positive Current Control Circuit High Bank 1 Sensor 1
What it means
P2239 means the ECM has detected a high voltage on the positive current-control circuit of the upstream (bank 1, sensor 1) wideband air-fuel oxygen sensor. This circuit is part of how the ECM drives and reads a modern air-fuel sensor, so the fault is electrical — the sensor or its wiring — rather than an actual mixture problem. The car still runs, but fueling accuracy suffers until it is repaired.
Can I keep driving? Drivable — the car runs, but with the upstream air-fuel sensor circuit faulted the fueling can be off, causing rough running and worse economy, so fix it before long.
Common symptoms
What you'll notice
- Check-engine light on
- Rough idle or running
- Engine surge or hunting
- Higher fuel consumption
Common causes
Most likely first
- Faulty upstream wideband (air-fuel) oxygen sensor, bank 1 sensor 1Likely
- Open or short to voltage in the sensor's positive current-control wiringCommon
- Poor or corroded connection at the O2 sensor connectorCommon
- Bad sensor ground or reference from the ECMLess often
How to diagnose & fix
Work through it in order
- Inspect the O2 sensor connector and wiring for corrosion, chafing, or loose pins.
- Check the positive current-control circuit for an open or a short to voltage, and confirm a clean ground and reference.
- Review the sensor's live data on a capable scan tool to confirm it is not responding correctly.
- Replace the bank 1 sensor 1 air-fuel/O2 sensor if the wiring checks good, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2239?+
Can I just clear P2239?+
Related codes
Often seen with P2239
Read & clear P2239 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.