OBD-II code · Powertrain (generic, extended)
P2270 O2 Sensor Signal Stuck Lean (Bank 1, Sensor 2)
The downstream oxygen sensor on bank 1 reports a constant lean signal during a forced-rich command from the ECU. Suggests either a sensor that has lost its rich-side response, or a catalyst that is so degraded that no rich exhaust reaches the downstream sensor (cross-check P0420).
Is it safe to drive with P2270?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyDownstream sensor failed stuck lean
- PossibleExhaust leak after catalyst
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–4 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Oxygen Sensor Downstream, Catalytic Converter
Related codes
- P2195O2 Sensor Signal Stuck Lean (Bank 1, Sensor 1)
- P2197O2 Sensor Signal Stuck Lean (Bank 2, Sensor 1)
- P2272O2 Sensor Signal Stuck Lean (Bank 2, Sensor 2)
- P226DParticulate Filter Deteriorated/Missing Substrate (Bank 1)
- P226EParticulate Filter Deteriorated/Missing Substrate (Bank 2)
- P226FTurbocharger Boost Control B Slow Response
- P2271O2 Sensor Signal Stuck Rich (Bank 1, Sensor 2)
- P2273O2 Sensor Signal Stuck Rich (Bank 2, Sensor 2)
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.