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Home >> Chevrolet >> 2002 >> Impala LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 3.8L >> Diagnostic Tests >> DTC P0401: EGR System Insufficient Flow >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Are any MAP DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Inspect exhaust system for modifications or leaks. Did you find and correct the condition? If yes, go to step  7. If no, go to next step.
  4. Check EGR valve gasket and pipes for leaks. Did you find and correct the condition? If yes, go to step  7. If no, go to next step.
  5. Remove EGR valve and check pintle, valve and passages for excessive deposits or restriction. Did you find and correct the condition? If yes, go to step  7. If no, go to next step.
  6. Remove EGR inlet and outlet pipes from exhaust and intake manifolds. Inspect manifold EGR ports and pipes for blockage or damage. Did you find and correct the condition? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  7. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within Conditions for Running DTC. Does DTC run and pass? If yes, go to next step. If no, go to step  2.
  8. Using scan tool, observe stored information. Does scan tool displays any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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