Circuit Description
WARNING: This page is about a different car, the 2002 Lexus ES 300. 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 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:
- Leak in exhaust system.
- Faulty A/F sensor.
- Faulty heated oxygen sensor No. 2.
- Faulty catalytic converter.