Oxygen sensor after the catalytic converter (sensor 2)

What it means

The second oxygen sensor sits after the catalytic converter. Its main job is to check that the converter is working. It has little effect on how the engine runs, so these codes rarely change how the car drives.

Codes in this group

Bank 1 is the side of the engine that has cylinder 1. Sensor 1 is before the catalytic converter and sensor 2 is after it. More terms explained.

What you may notice

• Usually only the warning light
• Possible failed emission test

Common causes

Most likely first:

• A worn-out sensor
• An exhaust leak near the sensor
• Damaged wiring under the car
• Water or corrosion in the connector

What to check first

• Look under the car for a wire hanging loose or melted on the exhaust
• Check for exhaust leaks
• Replace the sensor only after the wiring has been checked

Have a mechanic confirm. A fault code tells you which system reported a problem, not which part has failed. The same code can have several causes, and they differ between car models. Use this page to understand the code, then have a qualified mechanic test the car before any part is replaced.

After the repair

Once the cause is fixed, the code can be cleared with a scan tool, or the warning light goes out by itself after several trips without the fault. Clearing a code without fixing the cause only hides it for a while. More about clearing codes.

Related codes

Mass air flow (MAF) sensor (P0100), Manifold pressure (MAP) and barometric sensor (P0105), Intake air temperature sensor (P0110), Engine coolant temperature sensor (P0115), Thermostat and engine warm-up (P0125), Throttle position sensor (P0120), Accelerator pedal sensor and throttle agreement (P2120), Electronic throttle actuator (P2100). All codes.

Written in November 2026. These are generic OBD-II codes, the same on all makes. Causes and repair steps differ between models.