Circuit Description
WARNING: This page is about a different car, the 2000 Toyota Sienna. However, it is still accessible from the selected car via links, so may be relevant.
ECM compares waveform of heated oxygen sensor No. 1 (located before catalytic converter) with waveform of heated oxygen sensor No. 2 (located after catalytic converter) to determine if converter performance has deteriorated. If both waveforms change at similar rate, catalyst performance has deteriorated. DTC is set when all heated oxygen sensor waveforms have same amplitude after vehicle is driven for 5 minutes at 20-50 MPH. Possible causes are:
- Defective catalytic converter.
- Heated oxygen sensor circuit is open or shorted.
- Defective heated oxygen sensor.