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 Air/Fuel (A/F) sensor (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 A/F sensor and heated oxygen sensor No. 2 waveforms have same amplitude after vehicle is driven for 5 minutes at 20-50 MPH. Possible causes are:
- Defective catalytic converter.
- Heated oxygen sensor No. 2 circuit is open or shorted.
- Defective heated oxygen sensor No. 2.
- A/F sensor circuit is open or shorted.
- Defective A/F sensor.