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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 77 (Engine Controls Self-Diagnostics - 5.0L & 5,7L) >> Diagnostic Tests >> DTC P0401: EGR System - Insufficient Flow >> Diagnostic Procedures

Diagnostic Procedures

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  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Are there any MAP DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Observe the Freeze Frame/Failure Records data for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  4. Inspect the exhaust system for modification of original installed parts or leaks. Repair the exhaust system as necessary, if you locate a problem. Did you find and correct the condition? If yes, go to step  8. If no, go to next step.
  5. Check the EGR valve gasket and pipes for leaks. If you locate a problem, clean or replace the EGR system components as necessary. Perform Exhaust Gas Recirculation (EGR) System Cleaning. See appropriate SYSTEM & COMPONENT TESTING article. Did you find and correct the condition? If yes, go to step  8. If no, go to next step.
  6. Remove the EGR valve. Visually and physically inspect the following items for a leak or a restriction:
    • The EGR pintle
    • The EGR valve passages

    Did you find and correct the condition? If yes, go to step  8. If no, go to next step.

  7. Remove the EGR inlet and outlet pipes from the exhaust manifold and the intake manifold. Inspect the manifold EGR ports and the EGR inlet and outlet pipes for a blockage caused by excessive deposits or other damage. Did you find and correct the condition? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  8. Use the scan tool in order to clear the DTCs. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to step  2. If no, go to next step.
  9. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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