TorqueMech OBD Code Guide
P0157 - O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
Downstream O2 sensor signal voltage low (B2S2).
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Code Overview
Downstream O2 sensor signal voltage low (B2S2).
Common Causes
- Failing downstream oxygen sensor on bank 2 sensor 2
- Exhaust leak affecting the downstream reading
- Wiring fault or poor terminal contact in the sensor circuit
- Actual lean-running condition on bank 2
Symptoms
- Check-engine light with little or no drivability complaint
- Failed emissions readiness or inspection
- Downstream O2 data may stay low on the scan tool
Diagnostic Steps
- Inspect the bank 2 sensor 2 wiring and connector near the exhaust
- Check for exhaust leaks ahead of the downstream sensor
- Watch downstream sensor activity on the scan tool after warm-up
- Look for lean or catalyst-related companion codes before replacing the sensor
Repair Difficulty
Moderate
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