P2271 BMW Code - O2 Sensor Signal Biased/Stuck Rich Bank 1 Sensor 2

The P2271 code indicates that the downstream O2 sensor on Bank 1 (Sensor 2) is detecting a consistently rich air-fuel mixture, meaning excess fuel is present in the exhaust.

Symptoms may include poor fuel economy, rough idling, black smoke from the exhaust, a failed emissions test, and the check engine light being illuminated.

Common causes include a faulty O2 sensor, exhaust leaks, a rich-running engine due to a malfunctioning fuel injector, a failing mass air flow (MAF) sensor, or a defective catalytic converter.

While you may be able to drive the car, it is not recommended, as ignoring the issue can lead to further damage to the catalytic converter and increased emissions.

A technician will use an OBDII scanner to retrieve the code, inspect the O2 sensor and its wiring, check for exhaust leaks, and analyze fuel trims and air-fuel ratios for abnormalities.

Repairs may involve replacing the downstream O2 sensor, repairing exhaust leaks, cleaning or replacing the MAF sensor, fixing fuel system issues, or replacing the catalytic converter if it's damaged.

While unlikely, a severely clogged air filter can contribute to a rich air-fuel mixture, which may indirectly trigger the P2271 code.

Depending on the cause, repairs can range from $200 to $500 for a new O2 sensor or potentially more if major components like the catalytic converter need replacement.

Clearing the code will turn off the check engine light temporarily, but it won't resolve the underlying problem. The code will likely return if the issue isn't fixed.

A vacuum leak is more likely to cause a lean condition, not a rich condition. The P2271 code is typically related to excess fuel or a faulty O2 sensor.