P2251
O2 Sensor Negative Current Control Circuit/Open Bank 1 Sensor 1
Fuel & air metering (O2 sensor)
Generic OBD-II
Medium
What it means
P2251 means the negative pump-current control circuit for the bank 1, sensor 1 wide-band oxygen sensor is open or faulty. Wide-band air/fuel sensors rely on a small controlled current to measure the mixture accurately, so an open here leaves the ECM without a usable reading and upsets fuel trim. It's typically a broken wire, a corroded connector, or a failing sensor.
Medium
Can I keep driving? Drivable, but a faulty wide-band O2 sensor throws off fuel control, hurting economy and emissions and possibly causing rough running; repair soon.
Common symptoms
What you'll notice
- Check-engine light on
- Rough or uneven idle
- Increased fuel consumption
- Engine surge or hesitation
Common causes
Most likely first
- Faulty wide-band (air/fuel ratio) oxygen sensor on bank 1, sensor 1Likely
- Negative current-control wire open or brokenCommon
- Poor connection or corrosion at the O2 sensor connectorCommon
- Wiring damage where the harness routes near the exhaustLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check for companion bank 1 O2 codes (P2237, P2252).
- Inspect the bank 1 sensor 1 connector and wiring for corrosion, chafing, or a broken conductor.
- Check the negative current-control circuit for an open or high resistance against spec.
- Confirm the sensor's reference and ground circuits are intact.
- Replace the wide-band O2 sensor if the circuit tests good but the fault stays, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P2251?+
Yes for short trips, but fuel control and emissions are affected while it's active, so schedule the repair before longer driving.
Can I just clear P2251?+
You can, but an open in the current-control circuit or a failing sensor will set it again.
Related codes
Often seen with P2251
Read & clear P2251 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