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Home >> Lexus >> 1997 >> SC 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0420, P0430 - Catalyst System Efficiency Below Threshold >> Diagnosis & Repair

Diagnosis & Repair

  1. If any other codes are displayed other than DTC P0420 or P0430, diagnose and repair those codes first. If only DTC P0420 or P0430 is displayed, go to next step.
  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, replace catalytic converter and retest.
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