P0137 means O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2). The downstream oxygen sensor on bank 1, after the catalytic converter, is reading lower voltage than expected for too long. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0137 means
Oxygen sensors measure the oxygen left in the exhaust. Sensor 1 sits before the catalytic converter and is used for fuel control; sensor 2 sits after it and mainly monitors the converter. Most sensors have a heater so they start working soon after a cold start. A traditional zirconia sensor switches between about 0.1 volt (lean) and 0.9 volt (rich); many newer upstream sensors are wide-band air-fuel sensors that report differently, so check which type your engine uses.
P0137 symptoms
- Check engine light
- Usually no drivability change
Common causes of P0137
- Exhaust leak near the downstream sensor
- Failed sensor
- Wiring shorted to ground or chafed on the exhaust
- Real lean condition
How to diagnose P0137
- Check the exhaust for leaks around the sensor
- Inspect the wiring along the exhaust
- Check fuel trims for a real lean condition
- Watch the sensor signal on a scan tool
Can you drive with P0137?
Yes; repair it so the monitoring system works.
P0137 tips
Downstream sensor codes are often caused by an exhaust leak at a flange or a cracked pipe near the sensor, which pulls in outside air and makes the sensor read lean. Inspect the wiring along the exhaust as well, where heat damage is common.
Will P0137 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0137 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0138 | O2 Sensor Circuit High Voltage (Bank 1 Sensor 2) |
| P0141 | O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) |
| P0171 | System Too Lean (Bank 1) |
Guides that help
When it is more than a sensor
Oxygen sensor codes are fixed with a sensor, wiring, a fuse or an exhaust leak repair. An engine burning oil or coolant contaminates sensors quickly; if new sensors keep failing, check for blue or white exhaust smoke and a head gasket leak, and compare engines by code on our engines page if the engine is worn out.
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