The HO2S is used to supply the ECM with information regarding the composition of the air/fuel mixture. The HO2S is positioned in the exhaust pipe ahead of the TWC. To measure the oxygen content, the HO2S requires a supply of ambient air as a reference. Since this is supplied through the wiring, the lead must not be clamped or damaged in any other way. The HO2S produces a voltage that varies between 0.1V and 0.9V under normal operating conditions. The Engine Control Module (ECM) monitors this voltage and determines if the exhaust gas is lean or rich. If the voltage input at the ECM is under approx. 0.45V the exhaust is lean, and if the voltage input is over approx. 0.45V the exhaust is rich. The ECM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary.
If the HO2S signal’s reponse time from lean to rich(from rich to lean) is longer than 1.2 seconds, the ECM judged as a fault and DTC is set.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Response time from lean to rich (TLR) & from rich to lean (TRL) are monitored when A/F is intentionally changed. | ● Poor connection ● HO2S deteriorated ● Leak in exhaust system ● Defective ECM |
Enable Conditions | ● Closed loop ● Engine coolant > 49℃(120.2℉) ● Engine speed 1200~3000rpm ● Load value :25% ~ 60% | |
Threshold value | ● From lean to rich (TLR) > 1.2 sec ● From rich to lean (TRL) > 0.5 sec | |
Diagnosis Time | ● 8 sec continuous | |
MIL On Condition | ● 2 driving cycles |
