P0151 Oxygen sensor circuit low voltage (bank 2, sensor 1)
What P0151 means
The upstream oxygen sensor on bank 2 is reporting a voltage that stays too low, which normally means the exhaust looks lean. The engine computer cannot use it to control fuelling on that bank. Bank 2 is the side of a V6, V8 or boxer engine that does not contain cylinder 1.
P0151 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 60–350 €
- Workshop time
- 0.5–3 h
- Repair difficulty
- Medium
- DIY possible
- Yes
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine light on
- Higher fuel consumption
- Possible hesitation or rough idle
- Failed emissions test
Common causes
- Worn or contaminated upstream oxygen sensor on bank 2
- Exhaust manifold leak on bank 2 before the sensor
- Genuinely lean bank 2 from a vacuum leak or clogged injectors
- Signal wire shorted to ground
Can I keep driving with P0151?
You can keep driving, but have it checked within a week or two. The engine may use more fuel, and a long-standing upstream sensor fault can eventually harm the catalytic converter.
What to check first
- Compare bank 1 and bank 2 fuel trims: high positive trims on bank 2 only point to a lean condition on that side.
- Check the bank 2 exhaust manifold and front pipe for leaks.
- Inspect the sensor wiring for a short to ground.
- Replace the bank 2 upstream sensor if no leak or lean condition is found.
Related codes
- P0150 Oxygen sensor circuit (bank 2 sensor 1)
- P0152 Oxygen sensor circuit high voltage (bank 2, sensor 1)
- P0153 Oxygen sensor slow response (bank 2 sensor 1)
- P0155 Oxygen sensor heater circuit (bank 2, sensor 1)
- P0156 Oxygen sensor circuit (bank 2, sensor 2)
- P0157 Oxygen sensor circuit low voltage (bank 2, sensor 2)
- P0158 Oxygen sensor circuit high voltage (bank 2, sensor 2)
- P0160 Oxygen sensor circuit no activity detected (bank 2, sensor 2)
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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