An exhaust leak near the rear sensor (common). A failing rear oxygen sensor. A real lean condition.

P2270 O2 Sensor Signal Biased/Stuck Lean (Bank 1 Sensor 2)

Q: What does P2270 mean?

P2270 means bank 1's rear oxygen sensor won't read rich when tested, usually an exhaust leak or a lazy sensor. The rear oxygen sensor on bank 1 isn't reading rich when the engine computer briefly enriches the mixture to test it. It usually means the sensor is lazy or an exhaust leak is letting air in near it.

Oxygen sensors

P2270 means bank 1's rear oxygen sensor won't read rich when tested, usually an exhaust leak or a lazy sensor.

The rear oxygen sensor on bank 1 isn't reading rich when the engine computer briefly enriches the mixture to test it. It usually means the sensor is lazy or an exhaust leak is letting air in near it.

Can I keep driving? Yes, for now.

Safe to drive for now. It affects the catalytic converter check and emissions readiness.

Common causes

An exhaust leak near the rear sensor (common)
A failing rear oxygen sensor
A real lean condition

Symptoms

Check-engine light
Usually nothing else

What to check first

Check for exhaust leaks around the converter and rear sensor.
Watch the rear sensor during a snap of the throttle; it should go high.
Replace the sensor if there's no leak.

What does P2270 mean on your vehicle?

The likely cause depends on your engine. iRepair researches your exact year, make, model and engine (service bulletins, recalls and owner reports) and tells you what to check first. Your first 3 questions are free.

Ask iRepair about P2270

No scanner? Most auto parts stores read check-engine codes for free.

Related codes

General guidance for P2270 on most vehicles. Some makers use the same code a little differently; confirm in the service information for your vehicle, put safety first, and see a professional when in doubt.