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Home >> Oldsmobile >> 1997 >> Regency >> Repair and Diagnosis >> External Pages >> Different car >> Section 29 (Engine Control Systems Tests W/Codes) >> Diagnostic Trouble Codes >> DTC P0401 - EGR System Insufficient Flow >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 1998 Pontiac Bonneville, 1998 Oldsmobile Regency, 1998 Oldsmobile LSS, 1998 Oldsmobile Eighty-Eight, and 1998 Buick LeSabre. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Inspect exhaust system for modifications or leaks. Repair as necessary. After repairs, go to step 5). If no problem is found, go to next step.
  3. Remove EGR valve and check pintle, valve and passages and adapter for excessive deposits or restriction. Check EGR valve gasket and pipes for leaks. Repair as necessary. After repairs, go to step 5). If no problem is found, go to next step.
  4. Remove EGR inlet and outlet pipes from exhaust and intake manifolds. Inspect manifold EGR ports and pipes for blockage or damage. Repair as necessary. After repairs, go to next step. If no problem is found, see DIAGNOSTIC AIDS.
  5. Read and record FAIL RECORDS data for DTC P0401. Clear DTCs and monitor EGR TEST COUNT while operating vehicle within conditions noted in DIAGNOSTIC AIDS until 9-12 test counts have been taken. Read SPECIFIC DTC. If scan tool displays DTC P0401 TEST RAN AND PASSED, repair is complete. If scan tool does not display DTC P0401 TEST RAN AND PASSED, return to step 2).
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