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Home >> Toyota >> 2001 >> ECHO 2D Sedan, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold >> Diagnosis & Repair
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Diagnosis & Repair

  1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0420 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and then retest.
  2. Check exhaust system for leaks. If problem does not exist, go to next step. If problem exists, repair as necessary.
  3. Check heated oxygen sensor No. 1. See DTC P0130: HEATED OXYGEN SENSOR NO. 1 CIRCUIT . If problem does not exist, go to next step. If problem exists, repair as necessary.
  4. Check heated oxygen sensor No. 2. See DTC P0136: HEATED OXYGEN SENSOR NO. 2 CIRCUIT  test. If problem exists, repair as necessary. If problem does not exist, replace catalytic converter.
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