HO2S(S2) is in the rear side of Catalytic Converter to check the proper operation of catalyst. Oxygen density after the catalytic converter has to be within specific range (around 0.5V when there is no acceclation and deceleration.)
If the oxygen density changes in accordance with HO2S(S1), it means the poor performance of catalytic converter.
In case the sensor output is 0.4~0.52 V during 600sec or the internal resistance is over 40 ㏀ under enable conditions, ECM/PCM sets DTC P0136.( This DTC might be caused by the malfunction of Heater circuit, so, check the heater circuit first. )
Item | Detecting Condition | Possible Cause | |
DTC Strategy |
•
Signal check | 1. Poor connection 2. Open or short in signal circuit 3. S2 | |
General Enable Conditions |
•
Dew point end detected
•
Battery voltage > 11V
•
Exhaust Gas temperature = 662℉~1472℉ | ||
Case1 | ThresholdValue |
•
Sensor voltage : 0.4~0.52 V | |
DiagnosticTime |
•
600 sec | ||
Case2 | ThresholdValue |
•
Rate of heater pulse coupling to sensor signal > 5 times per every 10 heating pulses | |
MIL ON Condition |
•
2 driving cycle | ||
※ S2 : upstream oxygen sensor / S2 : downstream oxygen sensor
The amplitude of the signal output of the rear HO2S is small compared to the front HO2S because the rear HO2S detects emission gas purified by the catalytic converter. This is the normal signal waveform of the rear HO2S at idle.
