P0151 — O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
Drive with caution — fix soon.
What P0151 means
This code means the front oxygen sensor on bank 2 is reporting a steadily low voltage, which the computer reads as a constantly lean exhaust signal. It can be caused by a failing O2 sensor, wiring problems, a vacuum or exhaust leak, or an actual lean-running condition. It's a fairly common code and is often fixable once the source of the low reading is found.
Common symptoms
- Check engine light is on
- Rough idle or slight engine shaking
- Reduced fuel economy
- Hesitation or mild loss of power
- Possible lean-condition codes alongside it
Common causes
- Failing oxygen sensor (Bank 2 Sensor 1)
- Short to ground or open in the sensor wiring
- Vacuum leak causing a genuine lean condition
- Exhaust leak ahead of the sensor
- Low fuel pressure or a clogged fuel injector
Typical repair cost
$150 – $500
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0151 code?
For short trips, usually yes, but you shouldn't rely on it long term. Because this is the upstream sensor that helps set the fuel mixture, a lingering problem can mean rough running and worse mileage, so get it checked soon.
How much does it cost to fix a P0151 code?
Repairs typically range from $150 to $500. If it's just the oxygen sensor, you'll be near the lower end, but fixing a vacuum leak, exhaust leak, or fuel issue can raise the cost.
Is a P0151 code serious?
It's a moderate-severity code. It won't usually leave you stranded, but it affects how the engine manages fuel, so ignoring it can lead to drivability problems and higher emissions over time.
Could a P0151 code mean my engine is running lean?
Yes, a constant low voltage can reflect a genuinely lean exhaust, often from a vacuum leak, exhaust leak, or fuel delivery problem rather than the sensor itself. A technician will check those before condemning the O2 sensor.