P0138

DTC P0138 O2 Sensor Circuit High Input (Bank1, Sensor2)

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 detects the catalyst efficiency. The rear heated oxygen sensor (HO2S) produces a voltage between 0 V and 1 V. 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.

Detecting Condition & Limp Home:

DTC DETECTING CONDITION

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

2. Conditions for Setting the DTC

Schematic Diagram:

Signal Wave Form:

Step 1 - 3:

Inspection Procedure