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HOMESERVICE MANUALSOLDSMOBILE1998EIGHTY-EIGHT LSREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEMS TESTS W/CODESDIAGNOSTIC TROUBLE CODESDTC P0403 - EGR SOLENOID CONTROL CIRCUITDIAGNOSTIC PROCEDURES
1998 Oldsmobile Eighty-Eight LS

Diagnostic Procedures

1998 Oldsmobile Eighty-Eight LSSECTION Diagnostic Procedures
  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Start and operate engine at idle. Using scan tool, observe actual EGR position. If actual EGR position is zero percent, go to next step. If actual EGR position is not zero percent, go to step 9).
  3. Turn ignition on, engine off. Using scan tool select EGR VALVE OUTPUT CONTROL function. Increment EGR valve through all positions while comparing DESIRED EGR POSITION to ACTUAL EGR POSITION. If desired EGR position remains close to actual EGR position at all commanded positions, go to next step. If EGR position is not as specified, go to step 5).
  4. Using scan tool, review FAIL RECORDS data. Operate vehicle within FAIL RECORDS conditions and monitor SPECIFIC DTC info. If scan tool indicates that DTC P0403 failed this ignition cycle, go to next step. If scan tool does not indicate that DTC P0403 failed in this ignition cycle, see DIAGNOSTIC AIDS.
  5. Disconnect EGR valve harness connector. Using a test light, connect test light between EGR ground and control circuit at EGR harness connector. Using scan tool, command EGR valve to 100 percent. If test light illuminates, go to step 10). If test light does not illuminate, go to next step.
  6. Using test light connected to battery voltage, probe EGR ground circuit at EGR harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 14).
  7. Probe EGR control circuit at EGR harness connector. If test light illuminates, go to step 13). If test light does not illuminate, go to next step.
  8. Turn ignition off. Disconnect PCM harness connector. Check for open in EGR control circuit at PCM connector. Repair as necessary. After repairs, go to step 21). If circuit is okay, go to step 19).
  9. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, engine off. Using test light connected to ground, probe EGR control circuit at PCM connector. If test light illuminates, go to step 12). If test light does not illuminate, go to step 20).
  10. Check for poor terminal contact at EGR valve. Repair as necessary. After repairs, go to step 21). If terminals are okay, go to next step.
  11. Replace EGR valve. After replacing EGR valve, go to step 21).
  12. Locate and repair short to voltage in EGR valve control circuit. After repairs, go to step 21).
  13. Turn ignition off. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe EGR control circuit at EGR harness connector. If test light illuminates, go to step 18). If test light does not illuminate, go to step 17).
  14. Turn ignition off. Disconnect PCM harness connector. Using a test light connected to ground, probe EGR ground circuit at EGR harness connector. If test light illuminates, go to step 16). If test light does not illuminate, go to next step.
  15. Check for open in EGR valve ground circuit. Repair as necessary. After repairs, go to step 21). If circuit is okay, go to step 20).
  16. Locate and repair short to voltage in EGR valve ground circuit. After repairs, go to step 21).
  17. Check EGR valve control circuit for short to EGR ground circuit. Check for short between EGR valve control circuit and EGR pintle position sensor. Repair as necessary. After repair, go to step 21). If circuits are okay, go to step 20).
  18. Locate and repair short to ground in EGR valve control circuit. After repairs, go to step 21).
  19. Check circuits related to EGR valve for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 21). If terminal connections are okay, go to next step.
  20. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  21. 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).
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.