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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 379 (Engine Controls Self-Diagnostics - 3.4L) >> Diagnostic Tests >> DTC P0401: EGR System >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
  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, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Inspect the exhaust system for leaks, restrictions, and for modification of Original Equipment Manufacture (OEM) parts. See EXHAUST SYSTEM in SYSTEM & COMPONENT TESTING - 3.4L ALERO, GRAND AM, IMPALA & MONTE CARLO article. Did you find and correct the condition? If yes, go to step  7. If no, go to next step.
  4. Inspect 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. Inspect the EGR valve pintle and the EGR valve passages for leaks or for restrictions. See EXHAUST GAS RECIRCULATION under EMISSION SYSTEM & SUBSYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L ALERO, GRAND AM, IMPALA & MONTE CARLO 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. Inspect the exhaust manifold EGR port and the EGR valve pipe for a restriction. Did you find and correct the condition? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  7. Using scan tool, clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running. See CONDITIONS FOR RUNNING . Observe the EGR Flow Test Count parameter on the scan tool. 9-12 EGR Flow Test counts may be necessary to pass this DTC after the DTCs have been cleared. Did 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.
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