P0157O2 Sensor Circuit Low Voltage Bank 2 Sensor 2
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The oxygen sensor after the catalytic converter on bank 2 (sensor 2) is a switching sensor (about 0.1–0.9 V) used for converter monitoring and fine mixture trim. Bank 2 exists only on V and boxer engines with a separate downstream sensor per bank. P0157 means the signal stays below the lower limit, the bank 2 counterpart of P0137. GM sets it below 50 mV (two trips), on its 3.0 V6 within 50 s in closed loop; Ford uses its pull-up resistance check and counts both open circuit and short to ground as P0157. When it fails, the control module stops the downstream trim and cannot evaluate the converter; there is no limp mode.
- What you may notice
- Check engine light on (usually after two drive cycles)
- Catalyst monitor readiness not set
- Usually no noticeable change in driving
- Likely causes
- LikelySignal wire shorted to ground or melted against the exhaust
- LikelySensor faulty (cracked element, thermal shock from water)
- PossibleSignal circuit open (counts as low on Ford)
- PossibleExhaust leak ahead of the sensor (lean reading)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €60 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.