Circuit Description

ECM monitors heated oxygen sensor No. 2 located after converter to determine if converter performance has deteriorated. If converter is functioning properly, heated oxygen sensor waveform switches back and forth between rich and lean more slowly. DTC is set when A/F sensor and heated oxygen sensor No. 2 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.
• Defective Air/Fuel (A/F) Sensor.
• A/F sensor circuit is open or shorted.