P2249

O2 Sensor Reference Voltage Circuit Low Bank 2 Sensor 1

Q: Is it safe to drive with P2249?

Short-term yes, but with the air-fuel sensor reference faulted the ECM cannot trim fueling accurately, so the engine may run rough and use more fuel. Repair it before long trips.

Q: Can I just clear P2249?

It clears, but the low reference-voltage reading returns once the sensor circuit is monitored again. Fix the wiring or replace the sensor first.

Oxygen sensor circuit Generic OBD-II Medium

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.

Medium

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.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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?+

Short-term yes, but with the air-fuel sensor reference faulted the ECM cannot trim fueling accurately, so the engine may run rough and use more fuel. Repair it before long trips.

Can I just clear P2249?+

It clears, but the low reference-voltage reading returns once the sensor circuit is monitored again. Fix the wiring or replace the sensor first.

Read & clear P2249 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX