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 P0137 if the HO2S(B1S2) voltage remains excessively low for a predetermined time
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Voltage range check(short circuit to ground) | 1. Short to ground in signal harness 2. Poor connection or damaged harness 3. Faulty Heated O2 Sensor(HO2S) |
Enable Conditions |
•
Lambda close loop control active
•
Lambda controller not at max. limit
•
Catalyst purge after fuel cut-off not active
•
No relevant failure
•
10V< Battery voltage <16V | |
Threshold Value |
•
HO2S(B1S2) < 0.02V & Internal resistance < 15Ω | |
Diagnostic Time |
•
35 sec. | |
Mil On Condition |
•
2 Driving Cycles |
▶ Sector A : Signal Normal
▶ Sector B : Signal Fluctuation
▶ Sector C : Signal Recovery
