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.
ECM sets DTC P0150 if the ECM detects that the front HO2S signal circuit is open.
Item | Detecting Condition | Possible Cause | |
DTC Strategy | Case1) | ● Circuit malfunction | ● Open in signal harness ● Open in ground harness ● Contact resistance in connectors ● Faulty Heated O2 Sensor(HO2S) |
Case2) | ● Check time to closed loop control start with O2 sensor voltage | ||
Enable Conditions | Case1) | ● Sensor preheating and full heating phases finished ● Battery voltage >10V ● Lambda control active | |
Case2) | ● Battery voltage > 10V | ||
Threshold Value | Case1) | ● 0.37V < Sensor voltage < 0.54V (during 10 sec.) | |
Case2) | ● Time to closed loop control not activeated when O2 sensor voltage blocked between 0.37~0.54 V > 90~ 200 sec (depends on coolant temp. at start) | ||
Diagnostic Time | Case1) | ● 1 Sec. | |
Case2) | ● Immediate | ||
