04 6.6L Diesel High Pressure Fuel Line Leak after Repairs - kw LLY DTC torque GMT560 GMT800

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Certain 2004 6.6L LLY Duramax diesel engines may have an issue with the high pressure fuel lines that prevent them from achieving the proper torque upon reinstallation after a repair.

Complete proper SI procedures for Fuel Injector Feed Pipe Replacement. If a high pressure fuel line fails to achieve the proper torque or a fuel leak is encountered after fuel system repair, please complete a GMVIS on the vehicle and check the Engine Traceability Number. This traceability number is the engine unit number.

If the engine has a traceability/engine unit number of before 424514, the high pressure fuel line may need to be replaced. Engines built before the 424514 traceability/engine unit number may have a fuel line fitting with an outside diameter at the low end of the specification. When torque is applied to the fuel line nut, the sleeve between the fuel line nut and the fuel fitting may spread and not allow the proper torque to be reached. When this occurs, the technician may notice that the fuel line nut seems to be stuck to the fitting after the line is removed. This is due to the sleeve being expanded outward and interfering with the fuel line nut.

A new high pressure fuel line was released on all engines after the 424514 traceability/engine unit number. These engines should not have the torque or leak concerns. If a high pressure fuel line torque or leak concern is found after the 424514 traceability/engine unit number, inspect for excessive corrosion or debris on the high pressure line or fitting surfaces.

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

(04 LLY 6.6 C2 C3 K2 K3 Chevrolet Silverado GMC Sierra GMT800) and (04 LLY 6.6 C4 C5 D4 D5 E4 E5 Chevrolet Kodiak GMC Topkick GMT560)

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