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Home >> Toyota >> 2004 >> Matrix Base, FWD, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 16 (Engine Control System Self-Diagnostics - V6) >> 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 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
  1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0420 is displayed, go to next step. If other DTCs are displayed, diagnose and repair those DTCs first and retest system.
  2. Check exhaust system for leaks. If problem does not exist, go to next step. If problem exists, repair as necessary.
  3. Check A/F sensor circuits. See DTC P1130 OR DTC P1150: AIR/FUEL SENSOR CIRCUIT RANGE/PERFORMANCE . If problem does not exist, go to next step. If problem exists, repair as necessary.
  4. Check heated oxygen sensor No. 2 circuits. See DTC P0136: HEATED OXYGEN SENSOR NO. 2 CIRCUIT . If problem does not exist, replace exhaust pipe/catalytic converter assembly. If problem exists, repair as necessary.
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