P0151
O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1)
Same condition as P0131 but on bank 2. The upstream sensor sees a continuously lean exhaust on bank 2 or has a signal short to ground.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Common causes
Ordered by how often each turns out to be the cause.
- Exhaust leak upstream of the sensorCommon
- Bank 2 running lean (vacuum leak, fuel pressure)Possible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Oxygen Sensor Upstream
- Exhaust Pipe Pre Cat
P0151 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.