P0131

O2 Sensor Circuit Low Voltage Bank 1 Sensor 1

Oxygen sensor (fuel & air) Generic OBD-II Medium

What it means

P0131 means the upstream oxygen sensor on bank 1 (sensor 1) is reporting a persistently low voltage. That can mean the sensor or its wiring is faulty, or the exhaust is genuinely running lean. The ECM relies on this sensor to trim the air/fuel mixture, so the main effects are poorer fuel economy and higher emissions — the engine still runs and starts normally.

Medium

Can I keep driving? Yes — the car will run and start, but expect worse fuel economy and it will fail an emissions test until repaired.

Real-world scan data

Seen in

926

scans in the past year

Found in

0.1%

of scans

0.3%

of scans that found faults

Appears alongside · share of P0131 scans

P0171in 12.4% of scans

P0300in 11.7% of scans

P0130in 10.8% of scans

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
Poor fuel economy
Slight hesitation or rough running
Failed emissions/smog test

Common causes

Most likely first

Faulty upstream O2 sensor (bank 1, sensor 1)Likely
Signal wire shorted to ground or open in the O2 circuitCommon
Exhaust leak ahead of the sensor skewing the readingCommon
Genuine lean condition (vacuum leak or low fuel pressure)Less often
Failed ECM/PCM (rare)Less often

How to diagnose & fix

Work through it in order

View the bank 1 sensor 1 O2 voltage and fuel trims in live data to see whether the reading is stuck low or the engine is truly lean.
Inspect the O2 sensor wiring and connector for damage or a short to ground.
Check for exhaust leaks near the sensor and vacuum leaks that could cause a lean condition.
Confirm fuel pressure is in spec if trims show a real lean condition.
Replace the O2 sensor if it's faulty. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0131?+

Yes, short-term. The engine runs, but the ECM is working with a bad oxygen-sensor signal, so fueling and economy suffer. Fix it before an emissions test and to avoid wasting fuel.

Can I just clear P0131?+

It returns within a drive cycle or two unless the sensor, wiring, or underlying lean condition is repaired.

Read & clear P0131 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