DTC P0140-00: O2 Sensor Circuit No Activity Detected (Bank 1/Sensor 2): General Description

The rear Heated Oxygen Sensor (HO2S) 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 HO2S produces a voltage between 0V and 1V. This rear HO2S 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.