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Home >> Pontiac >> 1999 >> Firebird Formula, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - DTC P0352-P0452 >> DTC P0404 >> DTC P0404: EGR System Performance (5.7L "F" Body) >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
  2. Start and operate engine at idle. Using scan tool, command EGR valve to 50 percent. If engine runs rough or stalls, go to next step. If engine does not run rough or stall, go to step  4.
  3. Using scan tool, command EGR valve to 50 percent. Check if actual EGR position is within specified range. If EGR position is 48-52 percent, see DIAGNOSTIC AIDS . If actual EGR position is not within 48-52 percent, go to step  11.
  4. Turn ignition off. Disconnect EGR valve harness connector. Start and operate engine at idle. Using scan tool, command EGR to 100 percent. Using a test light connected to ground, probe EGR control circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step  6.
  5. Using a test light connected to battery voltage, probe EGR valve ground circuit. If test light illuminates, go to step  8. If test light does not illuminate, go to step  7.
  6. Check for open or short to ground in EGR control circuit. Repair as necessary. After repairs, go to step  12. If circuit is okay, go to step  10.
  7. Check for open in EGR ground. Repair as necessary. After repairs, go to step  12. If circuit is okay, go to step  10.
  8. Check terminal contact at EGR valve harness connector. Repair as necessary. After repairs, go to step  12. If contacts are okay, go to next step.
  9. Replace EGR valve. After replacing EGR valve, go to step  12.
  10. Check for poor connection or proper terminal contact at PCM. Repair as necessary. After repairs, go to step  12. If circuit is okay, go to next step.
  11. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  12. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0404. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool did not indicate that this test ran and passed, repeat step  2.
  13. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.
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