Circuit Description

Heated Oxygen Sensor (HO2S) produces a voltage that varies between -100 mV and 900 mV under normal operating conditions. Full operating range of HO2S circuit is about from -406 mV to 1124 mV. ECM monitors this voltage and determines if exhaust is lean or rich. Oxygen sensor voltage is high when exhaust is rich, and low when exhaust is lean. ECM constantly monitors HO2S signal during closed loop operation and compensates for rich or lean condition by decreasing or increasing injector pulse width as necessary. If oxygen sensor cannot cause voltage to swing below 350 mV or above 555 mV, this DTC will set.

Conditions for setting DTC:

• HO2S voltage stays between 350-555 mV for at least 3.5 seconds.
• HO2S voltage is greater than 200 mV for at least 200 milliseconds.