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.
The control unit of the linear oxygen sensor built inside the ECM monitors short circuit error on all front Heated Oxygen Sensor (HO2S) control lines and ECM sets P0151 with short circuit to ground.
ITEM | DETECING CONDITION | POSSIBLE CAUSE |
DTC Strategy | ●Sensor voltage low | ●Short to ground in signal harness ●Contact resistance in connectors ●Faulty Heated O2 Sensor.(HO2S) |
Enable Conditions | ●Sensor preheating and full heating phases finished ●Battery voltage ＞10V | |
Threshold Value | ●Sensor voltage ＜0.02V and element resistance ＜10Ω | |
Diagnostic Time | ●60 sec. | |
Fail Safe | ●Reset lambda adaptation and fuel trim adaptation. ●Front HO2S heater is controlled in open loop control. ●EVAP. Emission control function is controlled in minimum operation mode. |
