Circuit Description

The oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. The ECM uses this input signal to determine fuel injection system operation. Sensors include heater. DTC P0125 is set when sensor does not output a rich condition once engine is at normal operating temperature, engine speed is 1500 RPM or more, vehicle speed is at 25-62 MPH, throttle valve is not fully closed, at least 140 seconds has elapsed since engine has been started, and condition exists for at least 1.5 minutes. DTC P0125 is also set when vehicle runs out of fuel. Possible causes are:

• Fuel system fault.
• Fuel injectors.
• Ignition system fault.
• Exhaust gas leakage.
• Open or short in oxygen sensor circuit.
• Faulty heated oxygen sensor.