O2 Sensor Reference Voltage Circuit Low Bank 2 Sensor 1
What it means
P2249 means the ECM sees a low reference voltage on the upstream (bank 2, sensor 1) wideband air-fuel oxygen sensor circuit. This reference is part of how the ECM drives and reads a modern air-fuel sensor, so a low reading points to a wiring fault (short to ground or high resistance) or a failed sensor rather than an actual mixture problem. The engine 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 reference 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 2 sensor 1Likely
- Short to ground or high resistance in the sensor's reference voltage wiringCommon
- Poor or corroded connection at the O2 sensor connectorCommon
- Bad ground or reference feed from the ECMLess often
How to diagnose & fix
Work through it in order
- Inspect the bank 2 sensor 1 O2 connector and wiring for corrosion, chafing, or loose pins.
- Check the reference voltage circuit for a short to ground or high resistance, and confirm a clean ground.
- Review the sensor's live data on a capable scan tool to confirm it is not responding correctly.
- Replace the bank 2 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 P2249?+
Can I just clear P2249?+
Related codes
Often seen with P2249
Read & clear P2249 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.