Note. Sensor No. 1 refers to sensor located in exhaust manifold. Sensor No. 2 refers to sensor located behind catalytic converter.
Circuit Description
The ECM compares waveform of oxygen sensor located before catalytic converter with waveform of oxygen sensor located after converter to determine if converter performance has deteriorated. If both waveforms change at similar rate, catalyst performance has deteriorated. DTC is set when both oxygen sensors have same amplitude after vehicle is driven for 5 minutes at 20-50 MPH. Possible causes are
- Catalytic converter.
- Heated oxygen sensor open or short circuit.
- Heated oxygen sensor.