Note. Bank No. 1 refers to bank which includes cylinder No. 1. Bank No. 2 refers to bank without cylinder No. 1. Heated oxygen sensor No. 1 refers to sensor closest to engine block. Heated oxygen sensor No. 2 refers to sensor farthest from engine block.
Note. For component location, see appropriate illustration in THEORY & OPERATION article.
Circuit Description
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.
Diagnostic Aids
Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.