P0157 Oxygen sensor circuit low voltage (bank 2, sensor 2)
What P0157 means
The downstream oxygen sensor on bank 2, after the catalytic converter, is reporting a voltage that stays too low. The engine computer cannot use it to check the converter on that bank. Bank 2 is the side of a V6, V8 or boxer engine that does not contain cylinder 1.
P0157 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
- 80–350 €
- Workshop time
- 0.3–1.5 h
- Repair difficulty
- Easy
- 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
- Usually no noticeable change in how the car drives
- Catalyst readiness monitor not completing
- Possible failed emissions test at inspection
Common causes
- Worn or failed downstream oxygen sensor
- Exhaust leak near the sensor
- Signal wire shorted to ground
- Bank 2 running lean
Can I keep driving with P0157?
You can keep driving, but have it checked within one to two weeks. The engine is rarely affected, but the catalyst check cannot run and the car may fail its emissions inspection.
What to check first
- Look for exhaust leaks around the bank 2 catalytic converter and sensor.
- Check bank 2 fuel trims to rule out a lean condition.
- Inspect the sensor wiring for a short to ground.
- Replace the sensor if no leak or wiring fault is found.
Related codes
- P0156 Oxygen sensor circuit (bank 2, sensor 2)
- P0158 Oxygen sensor circuit high voltage (bank 2, sensor 2)
- P0155 Oxygen sensor heater circuit (bank 2, sensor 1)
- P0153 Oxygen sensor slow response (bank 2 sensor 1)
- P0152 Oxygen sensor circuit high voltage (bank 2, sensor 1)
- P0151 Oxygen sensor circuit low voltage (bank 2, sensor 1)
- P0150 Oxygen sensor circuit (bank 2 sensor 1)
- 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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