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Home >> Toyota >> 2004 >> Matrix Base, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 107 (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
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Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Lexus GS 430. However, it is still accessible from the selected car via links, so may be relevant.
  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 (bank 1, sensor 1 and bank 2, sensor 1). See HEATED OXYGEN SENSOR HEATER RESISTANCE under SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430, LS430 & SC430 article. Repair as necessary. If no problems are indicated, go to next step.
  3. Check heated oxygen sensor (bank 1, sensor 2 and bank 2, sensor 2). See HEATED OXYGEN SENSOR HEATER RESISTANCE under SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - GS300, IS300, GS430, LS430 & SC430 article. Repair as necessary. If oxygen sensor circuits are okay, replace catalytic converter and retest.
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