Circuit Description

The oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to ECM. 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 1400 RPM or more, vehicle speed is at 25-62 MPH, throttle valve is not fully closed, at least 180 seconds has elapsed since engine has been started, and condition exists for at least 65 seconds. DTC P0125 is also set when vehicle runs out of fuel. Possible causes are:

• Open or short in oxygen sensor circuit (bank No. 1 or 2, sensor No. 1).
• Faulty heated oxygen sensor (bank No. 1 or 2, sensor No. 1).
• Air induction system malfunction.
• Improper fuel system pressure.
• Fuel injectors.
• PVC hose connection.
• Exhaust gas leakage.
• Faulty ECM.