P2271 — O2 Sensor Signal Biased/Stuck Rich Bank 1 Sensor 2

P2271: O2 Sensor Signal Biased/Stuck Rich Bank 1 Sensor 2 — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

O2 Sensor Signal Biased/Stuck Rich Bank 1 Sensor 2. Basic catalogue definition; diagnostic details have not yet been reviewed.

Affected system: Powertrain

Symptoms

  • The engine warning light may be the only immediately visible symptom.
  • Rough running or hesitation can occur if fuelling is also affected.

Possible causes

  • The downstream oxygen sensor on bank 1 may be contaminated or biased toward a rich signal.
  • Damaged sensor wiring or excessive fuelling from a leaking injector may also contribute.

What to check

  • Confirm P2271 and locate bank 1, oxygen sensor 2.
  • Inspect the sensor wiring, terminals and visible contamination.
  • Review downstream-sensor readings with other fuelling data and related codes before deciding whether the sensor or fuel mixture is responsible.

Also written as: P2271-00, P227100 (some scan tools add the fault-type byte, e.g. -00).