P0137: O2 Sensor Circuit Low Voltage — Bank 1 Sensor 2
What to do
No urgent driveability impact. Ask for an exhaust leak check between the manifold and the rear sensor before the sensor is replaced.
What this code means
The downstream bank 1 sensor is reporting persistently low voltage. Because this sensor sits after the converter, a lean reading here often means air is entering the exhaust between the two sensors rather than that the mixture is lean — a corroded pipe, a failed flexible section, or a leaking gasket downstream of the manifold. Exhaust leaks are the leading cause on high-mileage vehicles.
Likely causes
Start here
- Exhaust leak before the sensor · moderate
- Faulty oxygen sensor · easy
Less common
- Wiring shorted to ground · moderate
- Road damage to underfloor wiring · moderate
- Corroded or loose connector · easy
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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