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Home >> Lexus >> 1998 >> SC 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Tests >> DTC P0420 Or P0430: Catalyst System >> Diagnosis & Repair

Diagnosis & Repair

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