P2270 — O2 Sensor Signal Stuck Lean (Bank 1, Sensor 2)

P2270 means the downstream oxygen sensor signal is stuck at a lean value. It's usually the sensor itself or an exhaust leak drawing air in behind the catalyst.

Cost range: $120–$700. Severity: low. Safe to drive? Yes. This is a monitoring fault rather than a driveability one.

Most common causes of P2270

1. Failed rear O2 sensor — Most likely cause on a high-mileage vehicle. ($120–$400)
2. Exhaust leak near the sensor — Rust-through at the mid-pipe. ($150–$600)
3. Sensor wiring damage — Heat or road debris damage under the car. ($80–$250)

Symptoms drivers report with P2270

• Check engine light
• Failed emissions
• No driveability change