GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 Engine Wiring Harness Assembly Replacement

Removal Procedure
  1. Remove the engine cover. Refer to Engine Cover Replacement in Interior Trim.

    2. Object Number: 786976 Size: SH
  2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  3. Remove the air cleaner Layer. Refer to Air Cleaner Replacement .
  4. Disconnect fuel injection control module connectors (1).

    5. Object Number: 664851 Size: SH
  5. Remove right side charged air cooler outlet duct.

    6. Object Number: 786973 Size: SH
  6. Disconnect the fuel filter/heater assembly connectors (1, 2).

    7. Object Number: 786980 Size: SH
  7. Disconnect the right rear fuel injector harness connector (1).

    8. Object Number: 788836 Size: SH
  8. Disconnect the exhaust gas recirculation (EGR) valve solenoid connector (1).

    9. Object Number: 788837 Size: SH
  9. Disconnect the EGR valve vent solenoid connector (1).

    10. Object Number: 788835 Size: SH
  10. Disconnect the EGR valve vacuum sensor (1).

    11. Object Number: 788838 Size: SH
  11. Disconnect the EGR throttle valve solenoid.

    12. Object Number: 788839 Size: SH
  12. Disconnect the electrical from right side glow plugs (1).

    13. Object Number: 788844 Size: SH
  13. Disconnect the right front fuel injector harness connector (1).

    14. Object Number: 788842 Size: SH
  14. Disconnect the turbo boost sensor connector (1).

    15. Object Number: 786983 Size: SH
  15. Remove the sight shield hold-down bracket (1).

    16. Object Number: 740506 Size: SH
  16. Disconnect the coolant temperature sensor (1).

    17. Object Number: 668427 Size: SH
  17. Remove the turbo water inlet hose.

    18. Object Number: 687052 Size: SH
  18. Remove the turbo coolant bypass valve.

    19. Object Number: 788845 Size: SH
  19. Remove the glow plug relay assembly.

    20. Object Number: 674653 Size: SH
  20. Disconnect the engine harness bulk connectors.

    21. Object Number: 674680 Size: SH
  21. Remove the bolts retaining bulk connectors to the bracket (1).

    22. Object Number: 664853 Size: SH
  22. Remove the left turbo charged air outlet hose.

    23. Object Number: 687021 Size: SH
  23. Remove the positive crankcase ventilation (PCV) hose from the left valve cover.

    24. Object Number: 786986 Size: SH
  24. Disconnect left front fuel injector harness connector (1).

    25. Object Number: 786988 Size: SH
  25. Disconnect the left rear fuel injector harness connector (1).

    26. Object Number: 786977 Size: SH
  26. Disconnect the fuel rail temperature sensor connector (1).

    27. Object Number: 788841 Size: SH
  27. Disconnect the glow plug controller connectors (1).

    28. Object Number: 788847 Size: SH
  28. Remove the fuel pipe retainer at the valve cover (2).

    29. Object Number: 788840 Size: SH
  29. Disconnect the electrical connectors from the left side glow plugs (1).

    30. Object Number: 788846 Size: SH
  30. Disconnect the oil level harness connector (1).

    31. Object Number: 739503 Size: SH
  31. Disconnect the barometric pressure (BARO) sensor connector (1).

    32. Object Number: 786994 Size: SH
  32. Disconnect the fuel rail pressure sensor connector (1).
  33. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  34. Remove the front lower skid plate.

    35. Object Number: 786970 Size: SH
  35. Disconnect the crankshaft position (CKP) sensor.

    36. Object Number: 742170 Size: SH
  36. Disconnect the camshaft position (CMP) sensor (1).

    37. Object Number: 786972 Size: SH
  37. Remove the bolts (1) retaining engine harness grounds.
  38. Lower the vehicle.

    39. Object Number: 786996 Size: SH
  39. Unroute and lift the engine wiring harness assembly for access to fuel rail pressure regulator.
  40. Disconnect the fuel rail pressure regulator (1).

    41. Object Number: 660421 Size: SH
  41. Remove the engine wiring harness from the vehicle.

Installation Procedure

    Object Number: 660421 Size: SH
  1. Install the engine wiring harness to the vehicle.

    2. Object Number: 786996 Size: SH
  2. Connect the fuel rail pressure regulator connector (1).
  3. Route the engine wiring harness to the engine.

    4. Object Number: 786972 Size: SH
  4. Raise the vehicle.

    5. Notice: Refer to Fastener Notice in the Preface section.

  5. Install the bolts (1) to retain the engine wiring harness grounds.

    6. Tighten
    Tighten the bolts to 34 N·m (25 lb ft).


    Object Number: 742170 Size: SH
  6. Connect the CMP sensor (1).

    7. Object Number: 786970 Size: SH
  7. Connect the CKP sensor.
  8. Install the front lower skid plate.
  9. Lower the vehicle.

    10. Object Number: 786994 Size: SH
  10. Connect the fuel rail pressure sensor connector (1).

    11. Object Number: 739503 Size: SH
  11. Connect the BARO sensor connector (1).

    12. Object Number: 788846 Size: SH
  12. Connect the oil level sensor harness connector (1).

    13. Object Number: 788840 Size: SH
  13. Connect the electrical connectors to left side glow plugs (1).

    14. Object Number: 788847 Size: SH
  14. Install the fuel pipe retainer (2).

    15. Tighten
    Tighten the nut to 8 N·m (70 lb in).


    Object Number: 788841 Size: SH
  15. Connect the glow plug controller connectors (1).

    16. Object Number: 786977 Size: SH
  16. Connect the fuel rail temperature sensor harness connector (1).

    17. Object Number: 786988 Size: SH
  17. Connect the left rear fuel injector harness connector (1).

    18. Object Number: 786986 Size: SH
  18. Connect the left front fuel injector harness connector (1).

    19. Object Number: 687021 Size: SH
  19. Install the PCV hose to valve cover.

    20. Object Number: 664853 Size: SH
  20. Install the left turbo charged air outlet hose.

    21. Object Number: 674680 Size: SH
  21. Install the bolts (1) to retain bulk connectors to the bracket.

    22. Object Number: 674653 Size: SH
  22. Connect the engine harness bulk connectors.

    23. Object Number: 788845 Size: SH
  23. Install the glow plug relay assembly.

    24. Object Number: 687052 Size: SH
  24. Install the turbo coolant bypass valve.

    25. Object Number: 668427 Size: SH
  25. Install the turbo water inlet hose.

    26. Object Number: 740506 Size: SH
  26. Connect the coolant temperature sensor (1).

    27. Object Number: 786983 Size: SH
  27. Install the engine sight shield hold-down bracket (1).

    28. Object Number: 788842 Size: SH
  28. Connect the turbo boost sensor (1).

    29. Object Number: 788844 Size: SH
  29. Connect right the front fuel injector harness connector (1).

    30. Object Number: 788839 Size: SH
  30. Connect the electrical connectors to the right side glow plugs (1).

    31. Object Number: 788839 Size: SH
  31. Connect the EGR throttle valve solenoid connector (1).

    32. Object Number: 788835 Size: SH
  32. Connect the EGR vacuum sensor (1).

    33. Object Number: 788837 Size: SH
  33. Connect the EGR vent solenoid (1).

    34. Object Number: 788836 Size: SH
  34. Connect the EGR valve solenoid (1).

    35. Object Number: 786980 Size: SH
  35. Connect the right rear fuel injector harness connector (1).

    36. Object Number: 786973 Size: SH
  36. Connect the fuel filter/heater assembly connectors (1, 2).

    37. Object Number: 664851 Size: SH
  37. Install the right turbo charged air hose.

    38. Object Number: 786976 Size: SH
  38. Connect the fuel injection control module connectors (1).
  39. Install the air cleaner layer. Refer to Air Cleaner Replacement .
  40. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  41. Install the engine cover. Refer to Engine Cover Replacement in Interior Trim.