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Home >> Toyota >> 2004 >> Matrix Base, FWD, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 15 (Engine Control System Self-Diagnostics - 4-Cylinder) >> Diagnostic Tests >> DTC P0420 Or DTC P0430: 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 and/or P0430 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 OR DTC P0156: HEATED OXYGEN SENSOR NO. 2 CIRCUIT . If problem exists, repair as necessary. If problem does not exist, replace exhaust manifold/catalytic converter assembly.
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