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Home >> Toyota >> 1998 >> Corolla CE, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes >> Self-Diagnostic Tests >> DTC P0420: Catalyst System Efficiency Below Threshold >> Diagnosis & Repair

Diagnosis & Repair

  1. If codes other than P0420 are present, diagnose and repair those codes first. If DTC P0420 is only displayed, check oxygen sensor No. 1. See DTC P0130: OXYGEN SENSOR CIRCUIT (SENSOR NO. 1) test. Repair as necessary. If oxygen sensor circuits are okay, go to next step.
  2. Check oxygen sensor No. 2 circuits. See DTC P0136 : OXYGEN SENSOR CIRCUIT (SENSOR NO. 2) test. Repair as necessary. If oxygen sensor circuits and sensor are okay, replace catalytic converter.
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