Monitor Description

To monitor the heated oxygen sensor (HO2S) activity, the ECM (PCM) performs the intrusive closed loop if the HO2S voltage does not exceed 0.45 V while the vehicle is running under the closed loop. In the intrusive closed loop, the ECM (PCM) varies the fuel trim and checks whether the HO2S voltage exceeds 0.45V or not.

Then, the HO2S voltage varies between 0.1 and 0.9 V when the HO2S functions. If the HO2S voltage does not exceed 0.45 V, the ECM (PCM) interprets this as a malfunction. The ECM (PCM) illuminates the MIL and sets the DTC (2 trip detection logic).