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

PCM sets DTC P0138 if the PCM detects signal voltage higher than the possible range of a properly operating rear heated oxygen sensor (HO2S).

DTC Detecting Condition

ITEM

DETECTING CONDITION

POSSIBLE CAUSE

DTC Strategy

●Check short circuit to battery on rear HO2S

● Short to Battery in signal harness

● Contact resistance in connectors

● Faulty Heated O2 Sensor(HO2S)

Enable Condition

● 10 ＜ Battery voltage ＜ 16V

Threshold Value

● Sensor voltage ＞1.3V

Diagnostic Time

● 1 sec.

Schematic Diagram
Signal Waveform
Яндекс.Метрика