FixVault
Home › Buick › 2003 › Century Base › Repair and Diagnosis › Engine Performance › System › Engine Controls Self-Diagnostics - 3.1L Engine › Diagnostic Tests › DTC P0401: EGR Flow Insufficient › Diagnostic Procedure

Diagnostic Procedure

  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. Is DTC P0107 or P0108 also set? If yes, diagnose appropriate DTC. Go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are set, go to next step.
  3. Check the exhaust system for leaks, restrictions, and for modification of Original Equipment Manufacture (OEM) parts. See EXHAUST SYSTEM CHECK under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 3.1L CENTURY, GRAND PRIX & MALIBU article. Did you find and correct the condition? If yes, go to step  7. If no, go to next step.
  4. Check for a vacuum leak between the EGR valve and the intake manifold. Did you find and correct the condition? If yes, go to step  7. If no, go to next step.
  5. Remove the EGR valve. Check the EGR valve pintle and the EGR valve passages for leaks or for restrictions. See EXHAUST GAS RECIRCULATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 3.1L CENTURY, GRAND PRIX & MALIBU article. Did you find and correct the condition? If yes, go to step  7. If no, go to next step.
  6. Remove the EGR valve inlet pipe from the exhaust manifold. Check the exhaust manifold EGR port and the EGR valve pipe for a restriction. Did you find and correct the condition? If yes, go to step  7. If no, go to DIAGNOSTIC AIDS .
  7. Using a scan tool, clear the DTCs. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running Test. See CONDITIONS FOR RUNNING TEST . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  8. Using the scan tool, observe the stored information in CAPTURE INFO. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
About FixVault