LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 1998 >> Forward Control P30, 6.5 F, Standard >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Engine Controls - Tests W/Codes - 5.7L) >> Diagnostic Trouble Codes >> DTC P0401 - EGR System Flow Insufficient >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different variant/trim than selected.
  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Install scan tool. Start engine. Using scan tool, select MISCELLANEOUS TESTS, EGR CONTROL and cycle EGR valve through 25, 50, 75 and 100 percent positions. Increase engine speed to greater than 1500 RPM. RPM should drop and engine should run rough as EGR valve is cycled. If engine runs rough as EGR valve is cycled, go to step 5). If engine does not run rough as EGR valve is cycled, go to next step.
  3. Turn ignition off. Disconnect EGR valve connector. Turn ignition on, with engine off. Connect test light between EGR control circuit and ignition feed circuit of EGR valve connector (engine harness side). If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
  4. Start engine. Using scan tool, select MISCELLANEOUS TESTS, EGR CONTROL and cycle EGR valve. With test light still connected, observe test light as EGR valve is cycled through 100 percent. If test light illuminates, go to step 8). If test light does not illuminate, go to step 11).
  5. Remove EGR valve and inspect for restrictions. Inspect if valve pintle is sticking partially open. If a problem is found, go to step 10). If no problem is found, go to next step.
  6. DTC is intermittent. Check if additional DTCs are set. If additional DTCs are set, diagnose affected DTCs. If not additional DTCs are set, see DIAGNOSTICS AIDS.
  7. Check for short to ground in EGR control circuit. If circuit is shorted, go to step 14). If circuit is okay, go to step 15).
  8. Check for a restriction in EGR tube or passage. If a problem is found, go to step 10). If no problem is found, go to next step.
  9. Check for poor connection at EGR valve. If connection is faulty, go to step 14). If connection is okay, go to next step.
  10. Replace EGR valve. After replacing EGR valve, go to step 16).
  11. Check for open in EGR control circuit. If circuit is open, go to step 14). If circuit is okay, go to next step.
  12. Check for open in ignition feed circuit. If circuit is open, go to step 14). If circuit is okay, go to next step.
  13. Check for poor connection at VCM. If a problem is found, go to next step. If no problem is found, go to step 15).
  14. Repair circuit as necessary. After repairs, go to step 16).
  15. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  16. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
  17. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTCs are displayed, go to applicable DTC test.
scientia non olet · About LEMON Manuals