DTC P2271: O2 Sensor Signal Stuck Rich (Bank 1 Sensor 2): General Description

The rear heated oxygen sensor is mounted either on the rear side of the Catalytic Convertor (warm-up catalytic Convertor) or in the rear exhaust pipe, is able to detect catalyst efficiency. The rear heated oxygen sensor (HO2S) produces a voltage between 0V and 1V. This sensor is used to estimate the oxygen storage capability. If a catalyst has good conversion properties, the oxygen fluctuations are smoothed by the oxygen storage capacity of the catalyst. If the conversion provided by the catalyst is low due to aging, poisoning or misfiring, then the oxygen fluctuations are similar to Signals from the front oxygen sensor.