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Diagnostic Procedure

DTC P0420 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 FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on repair order, then go to the next step.
2 VERIFY RELATED REPAIR INFORMATION AVAILABILITY 
  • Check for related Service Bulletins and/or online 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 OR STORED DTCS 
  • Turn ignition switch to OFF then ON (Engine off).
  • Verify related pending code or stored DTCs.
  • Are other DTCs present?
 Yes Go to appropriate DTC inspection.
No Go to the next step.
4 INSPECT GAS LEAKAGE OF EXHAUST SYSTEM 
  • Visually inspect exhaust gas leakage in exhaust system.
  • Is there gas leakage?
 Yes Repair or replace faulty exhaust parts, 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 sensor, then go to Step 7.
6 INSPECT TWC 
  • Clear DTC using the WDS or equivalent.
  • Cycle ignition switch to OFF then back to ON.
  • Inspect TWC.
  • Is it normal?
 Yes Replace suspected oxygen sensor, then go to the next step.
No Replace TWC, then go to the next step.
7 VERIFY TROUBLESHOOTING OF DTC P0420 COMPLETED 
  • Make sure to reconnect all disconnected connectors.
  • Turn ignition switch to ON (Engine off).
  • Clear the DTC from the memory using the WDS or equivalent.
  • Start engine and perform "PCM Adaptive Memory Procedure Drive Mode" and "EGR System Repair Verification Drive Mode".

    (See OBD-II DRIVE MODE ).

  • Is PENDING CODE for this DTC present?
 Yes Replace 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 inspection.
(See DTC TABLE ).
No Troubleshooting completed.
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