Circuit Description

The ECM compares waveform of the Air/Fuel Ratio Sensor (AFS) located in exhaust manifold with waveform of the heated 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 AFS and heated oxygen sensor waveforms have same amplitude after vehicle is driven within set vehicle and speed range. Possible causes are:

• Catalytic converter.
• Heated oxygen sensor open or short circuit.
• Heated oxygen sensor.
• AFS open or short circuit.
• AFS.