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Home >> Isuzu >> 1996 >> Hombre S >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Testing >> DTC P0401 - EGR System Insufficient Flow >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Start engine and allow it to idle. Using scan tool, command EGR valve to 50 percent. If engine stalls or runs rough, go to step 5). If engine dos not stall or run rough, go to next step.
  3. Turn ignition off. Remove EGR valve. Inspect EGR valve, passages and pipe for restriction or damage. Repair as necessary. After repair is completed, go to step 5). If no problems are found, go to next step.
  4. Replace EGR valve. After repair is completed, go to next step.
  5. Disconnect negative battery cable for 10 seconds, then reconnect cable. Road test vehicle. Increase vehicle speed to 60 MPH then release accelerator and allow vehicle to decelerate to 20 MPH. If Decel Exponentially Weighted Moving Average (EWMA) value is greater than zero, return to next step. If EWMA is zero or less, go to step 3).
    NOTE: For more information on Decel EWMA, see DIAGNOSTIC AIDS.
  6. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Operate vehicle within conditions required for setting this DTC. Select SPECIFIC DTC function then enter DTC P0401. If scan tool indicates TEST RAN AND PASSED, go to next step. If scan tool does not indicate TEST RAN AND PASSED, repeat step 2).
  7. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, no problem is indicated at this time.
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