Monitor Description

The ECM uses the HO2S to optimize the air-fuel mixture with closed-loop fuel control. This control helps decrease exhaust emissions by providing the catalyst with a nearly stoichiometric mixture. The sensor detects the oxygen level in the exhaust gas and the ECM uses this data to control the air-fuel ratio. The sensor output voltage ranges from 0.1 V to 0.9 V. If the signal voltage is less than 0.45 V, the air-fuel ratio is LEAN. If the signal voltage is more than 0.45 V, the air-fuel ratio is RICH. If the sensor does not indicate RICH even once despite the conditions for the closed-loop fuel control being met and the specified time period has passed, the ECM will conclude that the closed-loop fuel control is malfunctioning. The ECM will illuminate the MIL and a DTC is set.