P0139

DTC P0139 O2 Sensor Circuit Slow Responsive (Bank 1, Sensor 2)

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.

DTC Detecting Condition:

Schematic Diagram:

Signal Waveform:

Step 1 - 2:

Step 3 - 4:

INSPECTION PROCEDURE