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Home >> Pontiac >> 2002 >> Aztek AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0401: EGR System - Insufficient Flow >> Diagnostic Procedures
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Diagnostic Procedures

  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. 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  7. If no, go to next step.
  4. Check the EGR valve gasket and pipes for leaks. If you locate a problem, clean or replace the EGR system components as necessary. See EXHAUST GAS RECIRCULATION SYSTEM CLEANING under appropriate REMOVAL, OVERHAUL & INSTALLATION article. Did you find and correct the condition? If yes, go to step  7. If no, go to next step.
  5. 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  7. If no, go to next step.

  6. Remove the EGR inlet pipe from the exhaust manifold. Inspect the manifold EGR ports and the EGR inlet pipe for blockage caused by excessive deposits or other damage. Correct the condition as necessary if a problem is found. Did you find and correct the condition? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  7. Clear the DTCs with a scan tool. 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.
  8. 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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