P0157 — O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
The ECU detects abnormally low voltage from the downstream O2 sensor on bank 2. Indicates persistently lean exhaust past the catalyst, open sensor or wiring shorted to ground.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Oxygen sensor b2s2
- Oxygen sensor wiring
- Catalytic converter bank2
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Lean condition on bank 2
- Signal wire shorted to ground
- Downstream O2 sensor failed
Possible symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Related codes
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.