1. Open the hood.
2. Remove the air cleaner layer. Refer to Air Cleaner Replacement .



3. Remove the air intake pipe. Refer to Air Intake Pipe Replacement .
4. Disconnect the air conditioning (A/C) compressor clutch electrical connector.
5. Disconnect the A/C cut out switch electrical connector.
6. Remove the drive belt. Refer to Drive Belt Replacement in Engine Mechanical - 6.6L.
7. Remove the A/C compressor bolts.
8. Move the A/C compressor with the hoses attached to the right side of the engine compartment.



9. Remove the water outlet tube. Refer to Water Outlet Tube Replacement in Engine Cooling.
10. Disconnect both main harness electrical connectors.



11. Remove both main harness electrical connector to bracket bolts (1).
12. Remove the main harnesses from the bracket.



13. Disconnect the engine coolant temperature (ECT) sensor electrical connector (1).



14. Disconnect the barometric pressure (BARO) sensor electrical connector (1)



15. Disconnect the glow plug relay electrical connectors (1, 2, 3).



16. Disconnect the fuel rail temperature sensor electrical connector (1).



17. Disconnect the left front fuel injector electrical connector (1).



18. Disconnect the left rear fuel injector electrical connector (1).



19. Disconnect the fuel pressure regulator electrical connector (1).



20. Disconnect the oil level sensor harness electrical connector (1).



21. Remove the positive crankcase ventilation (PCV) hose from both valve covers.



22. Reposition the injection pump inlet clamp.
23. Remove the injection pump inlet hose from the fuel feed distribution (leak-off) block. Reposition the hose.



24. Clean the fuel pressure regulator and high pressure injection pump thoroughly with solvent, such as GM P/N 12377981 (Canadian P/N 10953463) or equivalent.
25. Using compressed air, thoroughly blow dry the regulator and pump.
26. Remove the 3 fuel pressure regulator screws (1) using a T25 TORX®.



27. Remove the fuel pressure regulator (1).
28. If dirt or debris is found in the bore or seating surfaces of the fuel injection pump, perform the following:

•	Place a clean rag over the bore on order to collect the excess fuel.

•	Bump the engine over in order to flush any debris out of the regulator bore.

Important: If the pressure regulator is being re-used, check the O-rings for damage. If the O-rings are damaged, install NEW O-rings.

1. Lubricate and install NEW O-rings onto the regulator. Lubricate the O-rings with clean, NEW engine oil.

Important: If the regulator is installed at an angle the O-rings may be damaged, resulting in possible fuel leakage.

2. Install the fuel pressure regulator (1).

Notice: Refer to Fastener Notice in the Preface section.




3. Install the 3 fuel pressure regulator screws (1) using a T25 TORX®.

Tighten

•	Tighten the screws a first pass to 4 N·m (35 lb in).

•	Tighten the screws a final pass to 7 N·m (62 lb in).




4. Install the injection pump inlet hose to the fuel feed distribution (leak) block.
5. Position the injection pump inlet clamp.



6. Install the PCV hose to both valve covers.



7. Connect the oil level sensor harness electrical connector (1).



8. Connect the fuel pressure regulator electrical connector (1).



9. Connect the left rear fuel injector electrical connector (1).



10. Connect the left front fuel injector electrical connector (1).



11. Connect the fuel rail temperature sensor electrical connector (1).



12. Connect the glow plug relay electrical connectors (1, 2, 3).



13. Connect the BARO sensor electrical connector (1)



14. Connect the ECT sensor electrical connector (1).



15. Install the main harnesses to the bracket.
16. Install both main harness electrical connector to bracket bolts (1).

Tighten
Tighten the bolts to 21 N·m (15 lb ft).




17. Connect both main harness electrical connectors.
18. Install the water outlet tube. Refer to Water Outlet Tube Replacement in Engine Cooling.



19. Position the A/C compressor.
20. Install the A/C compressor bolts.

Tighten
Tighten the bolts to 53 N·m (37 lb ft).

21. Install the drive belt. Refer to Drive Belt Replacement in Engine Mechanical - 6.6L.
22. Connect the A/C cut out switch electrical connector.
23. Connect the A/C compressor clutch electrical connector.
24. Install the air intake pipe. Refer to Air Intake Pipe Replacement .
25. Install the air cleaner layer, Refer to Air Cleaner Replacement .
26. Close the hood.