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Diagnosis & Repair

  1. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Start and run engine until normal operating temperature is reached. Ensure all accessories are off. Drive vehicle for 5-10 minutes at 31-40 MPH. Check for codes. If only DTC P0420 is displayed, go to next step. If other codes are displayed, diagnose and repair those codes first and retest system.
  2. Check heated oxygen sensor circuits. See DTC P0130: HEATED OXYGEN SENSOR FAULT (BANK NO. 1, SENSOR NO. 1), DTC P0150: HEATED OXYGEN SENSOR FAULT (BANK NO. 2, SENSOR NO. 1) circuit test. Replace oxygen sensors as necessary. If oxygen sensors are okay, go to next step.
  3. Check bank No. 1, sensor No. 2. See DTC P0136: HEATED OXYGEN SENSOR CIRCUIT (BANK NO. 1, SENSOR NO. 2). Replace oxygen sensor as necessary and retest system. If oxygen sensor is okay, replace catalytic converter and retest system.
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