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Home >> Nissan-Datsun >> 2021 >> NV2500 HD S >> Repair and Diagnosis >> External Pages >> Different car >> Section 209 (Engine Control System (DTC/Circuit Diagnosis) (CUMMINS 5.0L) (3 Of 6)) >> DTC/Circuit Diagnosis >> DTC P0421-00: Catalyst Efficiency Below Threshold >> Diagnosis Procedure

Diagnosis Procedure

WARNING: This page is about a different car, the 2018 Nissan Titan XD. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK DTC PRIORITY 
    1. Turn ignition switch ON.
    2. Connect CONSULT and check for "ENGINE" diagnostic trouble codes.
    3. Check for DTC P0421-00 being current on the CONSULT screen.

    Is DTC P0421-00 detected as current?

    YES

    GO TO 2 .

    NO

    Refer to Intermittent Incident .

  2. CHECK DTC PRIORITY 
    1. Turn ignition switch ON.
    2. Connect CONSULT and check for "ENGINE" diagnostic trouble codes.
    3. Are any of the following displayed as current on the CONSULT screen:
      • Any after treatment DOC temperature sensor or after treatment DPF temperature sensor DTCs
      • Any turbocharger DTCs
      • Any EGR valve DTCs
      • Any fuel system DTCs

    Is applicable DTC detected?

    YES

    Refer to DTC Index .

    NO

    GO TO 3 .

  3. CHECK EXHAUST SYSTEM FOR LEAKS 
    1. Turn ignition switch OFF.
    2. Inspect the exhaust system between the turbocharger outlet and the after treatment system:
      • Inspect for loose connections.
      • Inspect for leaking connections and broken exhaust system component.

    Is the inspection result normal?

    YES

    GO TO 4 .

    NO

    Repair or replace error-detected parts.

  4. INSPECT AFTER TREATMENT DOC 
    1. Remove the after treatment DOC from the vehicle. Refer to Removal and Installation .
    2. Inspect the after treatment DOC:
      • Plugging from soot or oil contamination
      • Soot plugging the front face of the catalyst

    Is the inspection result normal?

    YES

    GO TO 5 .

    NO

    Repair or replace the after treatment DOC.

  5. INSPECT TURBOCHARGER EXHAUST OUTLET 
    1. Remove the exhaust plumbing from the turbocharger outlet.
    2. Inspect the turbocharger exhaust outlet for signs of oil, coolant, or fuel being introduced into the after treatment system

    Is the inspection result normal?

    YES

    GO TO 6 .

    NO

    Locate and repair the cause of possible diesel fuel, coolant, or engine oil being carried from the engine into the after treatment system.

  6. INSPECT EXHAUST FOR EXCESSIVE BLACK SMOKE 
    1. Disconnect exhaust pipe from turbocharger outlet.
    2. Start the engine.
    3. Perform the Snap Acceleration - After treatment Disconnected procedure to check for excessive black smoke. Refer to Work Procedure .

    Is the inspection result normal?

    YES

    Inspection End.

    NO

    Refer to appropriate engine performance symptom table. Refer to Symptom Table .

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