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Home >> Cadillac >> 1998 >> Seville SLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0404 - EGR System Performance >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Turn ignition on. Using scan tool, check EGR pintle position. If scan tool displays 0.18-2.06 volts, go to next step. If scan tool does not display 0.18-2.06 volts, go to step 8).
  3. Using scan tool, select OUTPUT TESTS for EGR. Command EGR to zero percent. Check EGR pintle position display. If scan tool displays one volt or less, go to next step. If scan tool does not display one volt or less, go to step 20).
  4. Command EGR to 50 percent. Check EGR pintle position display. If scan tool displays 2-3 volts, go to next step. If scan tool does not display 2-3 volts, go to step 25).
  5. Command EGR to 100 percent. Check EGR pintle position display. If scan tool displays 4 volts, go to next step. If scan tool does not display 4 volts, go to step 22).
  6. Select FREEZE FRAME or FAILURE REC. Check EGR pintle position when DTC was set. If voltage reading is .18 volt or greater, go to next step. If voltage reading is not .18 volt or greater, go to step 21).
  7. If voltage reading is 5 volts or greater, go to step 24). If voltage reading is not 5 volts or greater, go to step 21).
  8. If voltage reading is .18 volts or less, go to next step. If voltage reading is not .18 volts or less, go to step 16).
  9. Exit OUTPUT TESTS. Using scan tool, check EGR pintle position. Disconnect EGR valve harness connector. Jumper EGR harness connector terminals "C" and "D". If voltage reading is .18 volts or less, go to next step. If voltage reading is not .18 volts or less, go to step 15).
  10. Using DVOM, check voltage between ground and jumper wire. If voltage reading is less than 4.5 volts, go to next step. If voltage reading is not less than 4.5 volts, go to step 26).
  11. Remove jumper wire. Check voltage between ground and EGR harness connector terminal "D". If voltage reading less than 4.5 volts, go to next step. If voltage reading is not less than 4.5 volts, go to step 27).
  12. Using scan tool, store fluid life data. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector. Disconnect TP sensor harness connector. Check resistance between ground and EGR harness connector terminal "D". If resistance is greater than 10,000 ohms, go to next step. If resistance is not greater than 10,000 ohms, go to step 28).
  13. Check resistance between PCM harness connector terminal No. 62 and EGR valve harness connector terminal "D". If resistance is less than 5 ohms, go to next step. If measured resistance is not less than 5 ohms, go to step 29).
  14. Check terminal contact at PCM harness connector C1 terminal No. 62. Repair as necessary. If terminal contact is okay, go to step 35).
  15. Check terminal contact at EGR harness connector. Repair as necessary. If terminal contact is okay, go to step 34).
  16. Exit OUTPUT TESTS. Using scan tool, check EGR pintle position. Disconnect EGR harness connector. If voltage reading is less than 2.06 volts, go to next step. If voltage reading is not less than 2.06 volts, go to step 30).
  17. Disconnect TP sensor and ECT sensor harness connectors. Using DVOM, check voltage between ground and EGR harness connector terminal "B". If voltage reading is 0.1 volt or less, go to next step. If voltage reading is not 0.1 volt or less, go to step 31).
  18. Check voltage between ground and EGR harness connector terminal "D". If voltage reading is 5.5 volts or less, go to next step. If voltage reading is not 5.5 volts or less, go to step 32).
  19. Store fluid life data. Turn ignition off. Wait 30 seconds, then disconnect PCM harness connector C1. Check resistance between PCM harness connector terminal No. 7 and EGR harness connector terminal "B". If resistance is less than 5 ohms, go to step 15). If resistance is not less than 5 ohms, go to step 33).
  20. Check for poor terminal contact at EGR harness connector and PCM harness connector C1. Check for high resistance in EGR pintle position ground, sticky EGR valve. Check for intermittent short to ground in EGR position feedback circuit, the 5-volt reference circuit and the EGR pintle position ground circuit. Repair as necessary. If circuits are okay, fault is not present.
  21. Check terminal contact at PCM and EGR harness connectors. Check for sticky EGR valve or debris in EGR system, causing EGR valve to stick. Repair as necessary. If repairs were not required, fault is not present.
  22. Check for terminal contact at PCM and EGR harness connectors. Check for high resistance in EGR position feedback circuit 5-volt reference circuit. Check for a sticky EGR valve. Repair as necessary. If repairs were not required, fault is not present.
  23. Check for intermittent opens or shorts to ground in 5-volt reference circuit and EGR position feedback circuit. Repair as necessary. If repairs were not required, fault is not present.
  24. Check for intermittent open in EGR pintle position ground circuit. Check for intermittent short to voltage in EGR position feedback circuit, EGR pintle position ground circuit or the 5-volt reference circuit. The reference circuit short may be located on any of the PCM 5-volt reference circuit (i.e. TP sensor 5-volt reference). Repair as necessary. If repairs were not required, fault is not present.
  25. Check for intermittent open or short in the ignition feed circuit and EGR valve control circuit. Check for a sticky EGR valve. Repair as necessary. If repairs were not required, fault is not present.
  26. Repair open in EGR position feedback circuit.
  27. Repair short to ground in EGR position feedback circuit.
  28. Repair short to ground in 5-volt reference circuit. Short may be located on any of the PCM 5-volt reference circuits (i.e. TP sensor 5-volt reference).
  29. Repair open in 5-volt reference circuit.
  30. Repair short to voltage in EGR position feedback circuit.
  31. Repair short to voltage in EGR pintle position ground circuit.
  32. Repair short to voltage in 5-volt reference circuit.
  33. Repair open in EGR pintle position ground circuit.
  34. Replace EGR valve.
  35. Replace PCM. Program replacement PCM using required equipment.
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