P2271: O2 Sensor Signal Stuck Rich (Bank 1, Sensor 2)
Standardized SAE J2012 code · P22xx — Fuel & air metering and auxiliary emission controls
What does P2271 mean?
The downstream oxygen sensor on bank 1 reports a constant rich signal during a forced-lean command. Suggests a failed downstream sensor or a sensor contaminated by oil/coolant from upstream engine wear.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Common causes
- High Downstream sensor failed stuck rich
- Medium Downstream sensor contaminated
Likelihood is a general estimate across vehicles; your make and model may differ.
Add your car to see reports of P2271 on the same make and model first.
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