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Home >> Mazda >> 2011 >> 2 Touring, 1.5 Z, Standard >> Repair and Diagnosis >> Engine Performance >> System >> On-Board Diagnostic [Engine Control System MZR 1.5] >> DTC P0421:00 >> Notes

DTC P0421:00: Notes

DTC P0421:00 (MZR 1.5) DETECTION CONDITION AND POSSIBLE CAUSES

DTC P0421:00 Warm up catalyst system efficiency below threshold
DETECTION CONDITION 
  • The PCM compares the number of A/F sensor and HO2S inversions for a predetermined time. The PCM monitors the number of inversions side performs while front side inverts for a specified number of times when the following monitoring conditions are met. The PCM detects inversion ratio. If the inversion ratio is below specification, the PCM determines that the catalyst system has deteriorated.

    MONITORING CONDITIONS 

    • Calculated TWC temperature: more than 400 °C {752 °F} 
    • Engine speed: 1,500-3,500 RPM 
    • LOAD: 15-48 % (at engine speed 2,000 RPM) 

    Diagnostic support note 

  • This is an intermittent monitor (catalyst).
  • The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
  • PENDING CODE is available if the PCM detects the above malfunction condition during first drive cycle.
  • FREEZE FRAME DATA (Mode 2)/Snapshot data is available.
  • The DTC is stored in the PCM memory.
POSSIBLE CAUSE 
  • Exhaust system leakage
  • A/F sensor looseness
  • HO2S looseness
  • TWC malfunction
  • PCM malfunction
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