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Home >> Toyota >> 1995 >> Tercel Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Testing >> Code P0420 - Catalyst System Efficiency Below Threshold >> Diagnosis & Repair
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Diagnosis & Repair

  1. Connect scan tester. See Figure. Start and warm engine to normal operating temperature. Drive vehicle at 31-40 MPH for 5-10 minutes. Stop vehicle. Retrieve codes. See RETRIEVING TROUBLE CODES .
  2. If codes other than P0420 are present, diagnose and repair those codes first. If Code P0420 is only displayed, inspect oxygen sensor circuits. See CODE P0130  - HEATED OXYGEN SENSOR (FRONT SENSOR) CIRCUIT. Repair systems as needed. If oxygen sensor circuits and sensors are okay, replace catalytic converter and retest.
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