| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. |
Note. Bank No. 1 refers to bank that includes cylinder No. 1. Bank No. 2 refers to bank without cylinder No. 2. Sensor No. 1 refers to sensor closest to engine block.
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, and at lease 140 seconds have 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.
- Fuel injectors.
- Ignition system.
- Exhaust gas leakage.
- Open or short in oxygen sensor circuit.
- Heated oxygen sensor.