Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval. Do not use a fault code alone to replace parts.
P0137: Oxygen sensor circuit low voltage, Bank 1 Sensor 2
The downstream Bank 1 sensor signal has remained below the range the computer expects.
What P0137 means
The downstream Bank 1 sensor signal has remained below the range the computer expects. Possible explanations include a low-biased sensor, a signal short to earth, an open or high-resistance circuit, an exhaust leak or a genuine engine mixture problem.
Can I still drive?
This is often not an immediate breakdown risk if the light is steady and the engine runs normally, but diagnosis should not be delayed. A genuine mixture or misfire fault can damage the catalyst. Stop for a flashing light, severe hesitation, judder, stalling or a strong fuel or burning smell.
Symptoms
- Engine-management light, often without a driving complaint
- Failed emissions or readiness test
- Rough idle, hesitation or poor economy if an underlying engine fault is present
- Unusual exhaust smell in some cases
Common causes
- Failed or contaminated downstream sensor
- Open, high-resistance or short-to-earth signal wiring
- Loose, wet or corroded connector
- Exhaust leak near or ahead of the sensor
- Extreme mixture fault, misfire or abnormal fuel pressure
Safe first checks
- Save stored and pending codes plus freeze-frame data. With the exhaust cold, inspect the sensor lead for heat damage, chafing and contamination, and check the plug for loose or corroded pins. Look for soot at accessible exhaust joints. Any live-data comparison should include related sensor and fuel-trim information under the maker's specified test conditions.
Typical UK fix cost
About £90–£350 for diagnosis and a usual wiring, leak or sensor repair. A simple sensor replacement typically benchmarks at £110–£266, but a wider fuelling or exhaust problem can cost more.
Related models
This is a generic OBD-II code used across many makes and models. The exact test thresholds, component layout and repair route vary by engine and manufacturer, so check vehicle-specific technical information before ordering parts.
Related fault codes
- P0135: Oxygen sensor heater circuit malfunction, Bank 1 Sensor 1
- P0136: Oxygen sensor circuit malfunction, Bank 1 Sensor 2
- P0138: Oxygen sensor circuit high voltage, Bank 1 Sensor 2
- P0140: Oxygen sensor circuit no activity detected, Bank 1 Sensor 2
Sources
A diagnostic trouble code identifies a system or circuit to investigate. It does not prove that a named part has failed. Preserve freeze-frame data and seek a vehicle-specific diagnosis before clearing the code.