P0159
O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)
The ECU detects an abnormally high voltage from the downstream O2 sensor on bank 2. Indicates persistently rich exhaust past the cat, shorted sensor or wiring shorted to voltage.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: easy
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.
- Rich condition on bank 2Common
- Signal wire shorted to voltagePossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Oxygen Sensor B2s2
- Oxygen Sensor Wiring
P0159 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.