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.
PCM sets DTC P0138 if the HO2S(B1S2) voltage remains excessively high for a predetermined time.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Voltage range check(short circuit to battery) | 1. Short to Battery in signal harness 2. Poor connection or damaged harness 3. Faulty Heated O2 Sensor(HO2S) |
Enable Conditions |
•
10V< Battery voltage <16V | |
Threshold Value |
•
1.2V< HO2S(B1S2) | |
Diagnostic Time |
•
1 sec. | |
Mil On Condition |
•
2 Driving Cycles |
▶ Sector A : Signal Normal
▶ Sector B : Signal Fluctuation
▶ Sector C : Signal Recovery
