P0137 Rear oxygen sensor voltage too low

By: Diagno editorial team · Updated: 2026-10-15

P0137 means: Rear oxygen sensor voltage too low. The rear oxygen sensor sits after the catalytic converter. OK to drive, but have it checked soon. The repair usually costs about €60–250 in Estonia. The most common cause: sensor is old or faulty. Other possible causes: wire or connector is damaged, exhaust leak.

What it means

The rear oxygen sensor sits after the catalytic converter. The engine computer uses it to check whether the converter is working. Often there is an exhaust leak or the wire is damaged.

What could be wrong

1. 1Sensor is old or faulty
2. 2Wire or connector is damaged
3. 3Exhaust leak
4. 4Catalytic converter is worn out

What you can check yourself

Check the sensor wire and connector. The wire often runs under the car and is easily damaged. You can check the simple things yourself, but the repair is best done in a workshop.

How we fix it

1. We check the sensor reading with a diagnostic tool
2. We check for exhaust leaks
3. We replace the sensor if it is faulty

Standard SAE description: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)