P0137: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)

P0137 means the downstream oxygen sensor on Bank 1 (post-catalyst, Sensor 2) is reporting a voltage that stays too low for too long. This typically indicates a lean exhaust condition reaching the sensor, an exhaust leak ahead of the sensor, or a failed sensor stuck at low voltage. The downstream sensor should read a relatively steady 0.6–0.8V when the catalytic converter is working properly.

P0137 is a emissions-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0137 and illuminates the check engine light.

If your vehicle has triggered P0137, you may notice one or more of these symptoms:

• Check engine light illuminated
• Slight increase in fuel consumption
• Possible failed emissions test
• Usually no noticeable change in how the car drives
• Often appears alongside P0420 if the converter is degrading

Here are the most common causes of P0137, ranked by how likely they are to be the culprit:

Generally yes, for short-term driving. Safe to drive short term. The downstream sensor does not directly control fuel mixture, but a persistent low signal often points to a damaged sensor, an exhaust leak, or a degrading catalytic converter. Do not delay repairs beyond a few weeks.

Follow these steps to pinpoint the root cause of P0137:

1. Read freeze frame data and check for any companion codes (P0420, P0171, P0174) that suggest a lean condition or converter problem
2. Inspect the exhaust system between the catalytic converter and the downstream sensor for cracks, loose clamps, or leaking gaskets
3. Inspect the Bank 1 Sensor 2 connector and wiring for corrosion, heat damage, or chafing
4. Use a scan tool to view downstream sensor voltage. A healthy sensor reads around 0.6–0.8V steady. A reading stuck below 0.2V points to sensor failure or an exhaust leak
5. Substitute a known-good sensor or swap with the Bank 2 downstream sensor if equipped. If the low voltage follows the sensor, the sensor is faulty

Repair costs for P0137 vary depending on the root cause and your vehicle. Here are typical estimates:

P0137 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0137 or indicate related issues: