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Home >> Lexus >> 1997 >> LX 450 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0420: Catalyst System Efficiency Below Threshold >> Diagnosis & Repair

Diagnosis & Repair

  1. Connect scan tool. 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 .
  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. Replace oxygen sensor as necessary. If oxygen sensors are okay, replace catalytic converter and retest.
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