General Information

Component Location





General Description

The rear heated oxygen sensor is mounted on the rear side of the Catalytic Converter (warm-up catalytic converter) or in the rear exhaust pipe, which is able to detect catalyst efficiency. The rear heated oxygen sensor (HO2S) produces a voltage between 0V and 1V. This rear heated oxygen 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.

DTC Description

The PCM tests rear O2 sensor signal level during the time the lambda target point is being shifted to lean to determine rear O2 sensor signal stuck. The PCM sets DTC P2271 if rear O2 sensor signal is above the predetermined threshold while target lambda point is being shifted to the predetermined value. If the same error code is set in the next driving cycle, the PCM illuminates the MIL.

DTC Detecting Condition





Diagnostic Circuit Diagram





Signal Waveform & Data




> Sector A : Signal Normal
> Sector B : Signal Fluctuation
> Sector C : Signal Recovery