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Diagnosis & Repair

  1. Retrieve trouble codes. See RETRIEVING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. If only DTC P0420 or P0430 is displayed, go to next step. If other codes are displayed, diagnose and repair those codes first and retest.
  2. Check for exhaust leaks. Repair as necessary. If exhaust system is okay, check heated oxygen sensor circuits (bank No. 1, sensor No. 1 and bank No. 2, sensor No. 1). See DTC P0130 OR DTC P0150: HEATED OXYGEN SENSOR CIRCUIT MALFUNCTION  test. Repair as necessary. If no problems are indicated, go to next step.
  3. Check heated oxygen sensor circuits (bank No. 1, sensor No. 2 and bank No. 2, sensor No. 2). See DTC P0136 OR P0156: HEATED OXYGEN SENSOR CIRCUIT MALFUNCTION  test. Repair as necessary. If oxygen sensor circuits are okay, replace catalytic converter and retest.
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