Circuit Description

The heated 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. DTC P0125 is set when oxygen 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, and at lease 140 seconds has elapsed since engine has been started, for at least 1.5 minutes. DTC P0125 is also set when vehicle runs out of fuel. Possible causes are:

• Fuel system.
• Injector.
• Ignition system.
• Exhaust system leakage.
• Open or short in oxygen sensor circuit.
• Heated oxygen sensor.