The heated oxygen sensor (HO2S) monitor tracks the rate of voltage change during the rise and fall of the HO2S signal. When the rate of voltage change is less than a calibrated value, the ECM/PCM begins to modify the fuel trim attempting to increase the HO2S voltage switch rate. This DTC sets when the ECM/PCM is at the allowable limit or has exceeded an allowable length of time for fuel trim modification, without etecting an acceptable rate of voltage change.
Item | Detecting Condition | Possible Cause | |
DTC Strategy | Case1 |
•
Switching Time check at entry in fuel cut off (Rich-to-Lean) [Switching time is measured between (down O2 signal entry in fuel cut off x 0.6) and (down O2 signal at entry in fuel cut off ×0.3)] | 1. Poor connection 2. HO2S(S2) 3. ECM/PCM |
Case2 |
•
Response Rate check after leaving fuel cut off (Lean-to-Rich) | ||
Enable Conditions | Case1 |
•
Downstream O2 sensor operative readiness detected * same as the conditions of P0136
•
Downstream O2 sensor pre-heating phase finished 2)
•
Catalyst temperature model > 400°C
•
Downstream O2 sensor signal at entry into fuel cut off > 0.6V
•
11V < Battery voltage < 16V | |
Case2 |
•
Downstream O2 sensor operative readiness detected * same as the conditions of P0136
•
Catalyst Purge after Fuel cut off active
•
Mass air flow integral after leaving fuel cut off > 130g
•
Catalyst temperature model > 400°C
•
Exhaust gas temperature model at sensor location > 400°C
•
O2 sensor internal resistance <= 10000Ω
•
11V < Battery voltage < 16V | ||
Threshold Value | Case1 |
•
Ratio (max. allowed switching time=360 ms) > 0.95 | |
Case2 |
•
Average of signal gradient < 1500mV/s | ||
Diagnostic Time | Case1 |
•
3 valid fuel cut-off phases | |
Case2 |
•
3 valid fuel cut-off phases | ||
MIL ON Condition |
•
2 driving cycles. | ||
※ S1 : upstream oxygen sensor / S2 : downstream oxygen sensor
