OBD-II code · Powertrain (generic)
P0137 O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
The downstream oxygen sensor signal is fixed at a low voltage. Either the catalyst is letting unburned oxygen through (sensor sees lean), the sensor itself is shorted to ground, or the catalyst is so degraded that the downstream signal mirrors a lean upstream condition.
Is it safe to drive with P0137?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- PossibleSignal wire shorted to ground
- PossibleCatalyst degraded (often appears before P0420)
- Less likelyExhaust leak between catalyst and downstream sensor
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–4 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Oxygen Sensor Downstream, Catalytic Converter
Related codes
- P0131O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
- P0151O2 Sensor Circuit Low Voltage (Bank 2, Sensor 1)
- P0134O2 Sensor Circuit No Activity / Slow Response (Bank 1 Sensor 1)
- P0135O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
- P0136O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)
- P0138O2 Sensor Circuit High Voltage (Bank 1, Sensor 2)
- P0139O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
- P013AO2 Sensor Slow Response - Rich to Lean Bank 1 Sensor 2
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.