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Home >> Buick >> 1996 >> Regal Base, 3.1 M >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 3.1L Engine >> Diagnostic Trouble Codes >> 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. Check exhaust system for modification of original parts. Also, check for exhaust leaks. Repair as necessary. After repair is completed, go to step 5). If exhaust is okay, go to next step.
  3. Remove EGR valve. Inspect EGR valve pintle, valve passages and adapter for excessive deposits or restrictions. Repair as necessary. After repair is completed, go to step 5). If no problems are found, go to next step.
  4. Remove EGR inlet and outlet pipes from exhaust manifold and intake manifold. Inspect manifold EGR ports and EGR pipes for blockage. Repair as necessary. After repair is completed, go to next step. If no problems are found, see DIAGNOSTIC AIDS.
  5. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Ensure engine is at normal operating temperature. Monitor EGR TEST COUNT display while operating vehicle as specified. See DIAGNOSTIC AIDS. Continue operating vehicle EGR TEST COUNT until 9-12 test samples have been taken. Select SPECIFIC DTC function then enter DTC P0401. If scan tool indicates TEST RAN AND PASSED, repair is completed. If scan tool does not indicate TEST RAN AND PASSED, go to step 2).
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