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Home >> Toyota >> 2003 >> Matrix Base, FWD, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 86 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold >> Diagnosis & Repair
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Diagnosis & Repair

WARNING: This page is about a different car, the 2003 Lexus RX 300. However, it is still accessible from the selected car via links, so may be relevant.
  1. If other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P0420 is displayed, go to next step.
  2. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, go to next step.
  3. Check A/F sensor No. 1 and No. 2 circuits. See AIR/FUEL (A/F) SENSOR HEATER RESISTANCE in SYSTEM & COMPONENT TESTING - ES300 & RX300 article and ENGINE PERFORMANCE in WIRING DIAGRAMS article in ELECTRICAL. If problem exists, repair as necessary. If problem does not exist, go to next step.
  4. Check heated oxygen sensor No. 2 circuits. See DTC P0136: HEATED OXYGEN SENSOR CIRCUIT FAULT (BANK 1 SENSOR 2) . If problem exists, repair as necessary. If problem does not exist, replace catalytic converter.
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