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Home >> Chevrolet >> 1996 >> Astro Van Cargo, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0401 - EGR System Insufficient Flow >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. Start and warm engine to normal operating temperature. Run engine at greater than 1500 RPM. Using scan tool, command EGR duty cycle through 25, 50, 75 and 100% positions. If engine runs rough as EGR is cycled, go to step 5). If engine does not run rough, go to next step.
  3. Turn engine off. Turn ignition on, engine off. Disconnect EGR valve harness connector. Connect a test light between EGR valve harness connector ignition feed and control circuits. If test light does not illuminate, go to next step. If test light illuminates, go to step 7).
  4. Start engine. Using scan tool, select MISCELLANEOUS TESTS, EGR CONTROL. With test light still connected, command EGR duty cycle increase to 100 percent. If test light illuminates as EGR is cycled, go to step 8). If test light does not illuminate, go to step 11).
  5. Remove EGR valve and inspect valve and passages for damage. Inspect valve pintle to ensure it is not sticking partially open. If a problem is found, go to step 10). If no problem is found, go to next step.
  6. Go to DIAGNOSTIC AIDS.
  7. Check for short to ground in EGR valve control circuit. If short is found, go to step 14). If no short is found, go to step 15).
  8. Check for restriction in EGR tube or passage. If restriction is found, go to step 10). If no restriction is found, go to next step.
  9. Check for faulty electrical connection at EGR valve. If faulty connection is found, go to step 14). If connection is okay, go to next step.
  10. Replace faulty EGR valve and go to step 16).
  11. Check for an open in EGR control circuit. If an open is found, go to step 14). If an open is not found, go to next step.
  12. Check for an open in EGR ignition feed circuit. If an open is found, go to step 14). If an open is not found, go to next step.
  13. Check for faulty connection at VCM. If faulty connection is found, go to next step. If connection is okay, go to step 15).
  14. Repair circuit as necessary and go to step 16).
  15. Replace VCM. Program replacement VCM using required equipment. After repair is completed, go to next step.
  16. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter DTC P0401. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, return to step 2).
  17. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.
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