General Information

Engine Control
P2270 O2 Sensor Signal Stuck Lean (Bank 1 Sensor 2) - 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

ECM set P2270 code if output signal is too low at DOWN O2 sensor when AIR-FUEL ratio is under thick condition.

DTC Detecting Condition





Diagnostic Circuit Diagram










Signal Waveform and Data




If you release the accelerator pedal suddenly after engine running about 4000 rpm, fuel supply will stop for short period and the O2 sensor service data in the Hi-Scan (Pro) will display values 200mV or lower. When you suddenly press on the accelerator pedal down, the voltage will reach 0.6 - 1.0 V. When you let the engine idle again, the voltage will fluctuate between 200 mV or lower and 0.6 - 1.0 V. In this case, the O2sensor can be determined as good.