FixVault
Home › Mazda › 2011 › 3 i SV, 2.0 F › Repair and Diagnosis › Engine Performance › System › On-Board Diagnostic [Engine Control System LF, L5] › DTC P0421:00

DTC P0421:00

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 HO2S inversion counts when the following conditions are met. The PCM detects inversion ratio. If the inversion ratio is below specification, the PCM determine that the catalyst system has deteriorated.
    • The A/F sensor inversion counts is as prescribed when the following monitoring conditions are met:
    • The accumulated occurrence time of the following monitoring conditions has exceeded the prescribed time limit:

    MONITORING CONDITIONS 

    • Catalyst converter temperature: more than 400°C {752 CF}
    • Engine speed:
      • 1, 350-3, 000 rpm (LF/ATX) 
      • 1, 500-3, 000 rpm (LF/MTX) 
      • 1, 200-3, 000 rpm (L5/ATX) 
      • 1, 300-3, 000 rpm (L5/MTX) 
    • Charging efficiency: 15-48 %  (engine speed: 2, 000 rpm)

Diagnostic support note 
  • This is an intermittent monitor (catalyst).
  • The MIL illuminates if PCM detects above malfunction condition in two consecutive drive cycles or in one drive cycle while DTC for the same malfunction has been stored in PCM.
  • PENDING CODE is available if 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 loose
  • HO2S loose
  • TWC malfunction
  • PCM malfunction
DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 VERIFY FREEZE FRAME DATA (MODE 2)/SNAPSHOT DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED 
  • Have the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS (catalyst related) been recorded?
 Yes Go to the next step.
No Record the FREEZE FRAME DATA (Mode 2)/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
2 VERIFY RELATED REPAIR INFORMATION AVAILABILITY 
  • Verify related Service Bulletins and/or on-line repair information availability.
  • Is any related repair information available?
 Yes Perform repair or diagnosis according to the available repair information.
  • If the vehicle is not repaired, go to the next step.
No Go to the next step.
3 VERIFY RELATED PENDING CODE AND STORED DTC 
  • Switch the ignition to off, then to ON (engine off).
  • Perform the DTC Reading Procedure and Pending Trouble Code Access Procedure.

    (See ON-BOARD DIAGNOSTIC TEST ).

  • Are any other DTCs present?
 Yes Go to the applicable DTC inspection.
(See DTC TABLE ).
No Go to the next step.
4 INSPECT FOR LEAKAGE FROM EXHAUST SYSTEM 
  • Visually inspect the exhaust gas system.
  • Is there any leakage?
 Yes Repair or replace the malfunctioning part according to the inspection results, then go to Step 8.
No Go to the next step.
5 INSPECT INSTALLATION OF A/F SENSOR 
  • Inspect the A/F sensor for looseness.
  • Is the A/F sensor installed securely?
 Yes Go to the next step.
No Retighten the A/F sensor, then go to Step 8.
(See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION ).
6 INSPECT INSTALLATION OF HO2S 
  • Inspect the HO2S for looseness.
  • Is the HO2S installed securely?
 Yes Go to the next step.
No Retighten the HO2S, then go to Step 8.
(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION ).
7 INSPECT TWC 
 Yes Replace the TWC, then go to the next step.
(See EXHAUST SYSTEM REMOVAL/INSTALLATION ).
No Go to the next step.
8 VERIFY DTC TROUBLESHOOTING COMPLETED 
  • Make sure to reconnect all disconnected connectors.
  • Clear the DTC from the PCM memory using the M-MDS.

    (See AFTER REPAIR PROCEDURE ).

  • Perform the Drive Mode 03 (EGR System, A/F sensor heater, HO2S heater, A/F sensor, HO2S and TWC Repair Verification Drive Mode).

    (See OBD-II DRIVE MODE ).

  • Is the PENDING CODE for this DTC present?
 Yes Repeat the inspection from Step 1.

Go to the next step.
No Go to the next step.
9 VERIFY AFTER REPAIR PROCEDURE 
 Yes Go to the applicable DTC inspection.
(See DTC TABLE ).
No DTC troubleshooting completed.
About FixVault