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Home >> Toyota >> 1996 >> Previa DX, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes >> Circuit Tests >> DTC 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 SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.
  2. If codes other than P0420 are present, diagnose and repair those codes first. If DTC P0420 is only displayed, check oxygen sensor. See SYSTEM/COMPONENT TESTS article. Repair as necessary. If oxygen sensors are okay, replace catalytic converter and retest.
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