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Home >> Lexus >> 2003 >> LS 430 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1) Or DTC P0430: Catalyst System Efficiency Below Threshold (Bank 2) >> Diagnosis & Repair

Diagnosis & Repair

  1. Retrieve trouble codes. See RETRIEVING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. If only DTC P0420 or P0430 is displayed, go to next step. If other codes are displayed, diagnose and repair those codes first and retest.
  2. Check for exhaust leaks. Repair as necessary. If exhaust system is okay, check heated oxygen sensor circuits (bank 1, sensor 1 and bank 2, sensor 1). See HEATED OXYGEN SENSOR OPERATION in SYSTEM & COMPONENT TESTING article. Repair as necessary. If no problems are indicated, go to next step.
  3. Check heated oxygen sensor circuits (bank 1, sensor 2 and bank 2, sensor 2). See DTC P0130, DTC P0150, DTC P2195, DTC P2196, DTC P2197 & DTC P2198 . Repair as necessary. If oxygen sensor circuits are okay, replace catalytic converter and retest.
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