P2271O2 Sensor Signal Biased/Stuck Rich (Bank 1, Sensor 2)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P2271 is the opposite fault of the same bank 1 rear sensor: its voltage refuses to fall when the exhaust should be lean. It is usually checked during a deceleration fuel cut, when almost pure air passes the sensor. GM's 2018 four-cylinders set it if the signal is still above 100 mV after 25 g of air in fuel cut-off (Type B); GM's Bosch-based 2005 V6 looks for a reading above 0.2 V four seconds into the cut, VW's 2014 data books for CC and Tiguan use 0.15 V after 3000 mg of oxygen, and Ford added a fuel-cut stuck test from model year 2019. Causes are a sensor poisoned by coolant, oil or silicone, a signal wire touching voltage, or a front sensor misleading the ECM; Honda traced this on the 2007 to 2008 Acura TSX and replaced both sensors. P2097 and P0138 cover trim and circuit.
- What you may notice
- Malfunction indicator lamp on
- Catalyst monitor not completing
- Likely causes
- LikelyRear oxygen sensor contaminated by coolant, oil or silicone
- PossibleFaulty front A/F sensor making the rear sensor look stuck rich
- RareSignal wire chafed against a voltage source
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €60 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.