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Home >> Mazda >> 2006 >> 5 Touring, 2.3 L >> Repair and Diagnosis >> Engine Performance >> System >> On-Board Diagnostic [Engine Control System L3) >> DTC P0421 >> Diagnostic Procedure
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Diagnostic Procedure

DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED 
  • Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (Catalyst related) been recorded?
 Yes Go to the next step.
No Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on repair order, then go to the next step.
2 VERIFY RELATED SERVICE INFORMATION AVAILABILITY 
  • Verify related Service Information availability.
  • Is any related Service Information available?
 Yes Perform repair or diagnosis according to the available Service Information.
  • If the vehicle is not repaired, go to the next step.
No Go to the next step.
3 VERIFY RELATED PENDING CODE OR STORED DTC 
  • Turn the ignition switch off then to the ON position (Engine off).
  • Verify related pending code or stored DTCs.
  • Are other DTCs present?
 Yes Go to .
No Go to the next step.
4 INSPECT GAS LEAKAGE OF EXHAUST SYSTEM 
  • Visually inspect exhaust gas leakage in the exhaust system.
  • Is there gas leakage?
 Yes Repair or replace the malfunctioning exhaust part, then go to Step 7.
No Go to the next step.
5 INSPECT INSTALLATION OF FRONT AND REAR OXYGEN SENSORS 
  • Inspect for looseness of front and rear oxygen sensors.
  • Is it normal?
 Yes Go to the next step.
No Retighten the sensor, then go to Step 7.
6 INSPECT TWC  Yes Replace the heated oxygen sensor, then go to the next step.
No Replace the TWC, then go to the next step.
7 VERIFY TROUBLESHOOTING OF DTC P0421 COMPLETED 
  • Make sure to reconnect all disconnected connectors.
  • Turn the ignition switch to the ON position (Engine off).
  • Clear the DTC from the memory using the WDS or equivalent.
  • Perform the HO2S heater, HO2S, and TWC Repair Verification Drive Mode.

    (See OBD-II DRIVE MODE ).

  • Is the PENDING CODE for this DTC present?
 Yes Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION ).
No Go to the next step.
8 VERIFY AFTER REPAIR PROCEDURE  Yes Go to the applicable DTC troubleshooting.
(See DTC TABLE ).
No Troubleshooting completed.
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