There was a TSB from GM about the P0087 code-- The problem was weak fuel hose where the lines are connected above the transmission. The hose collasped or was kinked, and restricted the fuel flow. Posted the TSB -may help.
#PIP4526: Diesel Engine Fuel Line Repairs - keywords DTC hose kink loss P0087 P0093 P1093 pipe power reduced repair restrict restriction SES suction supply vacuum - (Nov 7, 2008)
Subject: Diesel Engine Fuel Line Repairs
Models: 2001-2007 Chevrolet Silverado Classic
2001-2007 GMC Sierra Classic
2007-2009 Chevrolet Silverado
2007-2009 GMC Sierra
Equipped with the 6.6L Diesel Engine RPO codes LB7 LBZ LLY LMM
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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
A dealer may need to perform a repair on the rubber portion of the fuel supply (suction) lines. The rubber section of the line could become kinked or collapse. Fuel lines that kink or collapse may induce a fuel system restriction (high vacuum gauge readings) or DTCs P0087, P0093, and/or P1093 to set.
If a technician was to suspect the rubber portion of the fuel feed line collapsing or kinking, replacement of only the rubber line is acceptable.
Recommendation/Instructions:
Complete the steps below to repair the rubber section of fuel supply line:
Carefully cut, split, and remove the OEM crimp from both ends of the flexible hose. These crimps can be cut with a small cut-off wheel. Split the crimp into two pieces (use your discretion on first cut location, then cut directly across from, or 180 degrees from first cut). Special care must be taken not to damage the flare on the end of the steel pipe that will be reused.
Remove the OEM crimps and flexible portion of hose from the existing supply line.
If replacing the rubber section of the supply line, a 1/2 ID hose meeting SAE specification 100R3 is suggested. Dealers may be able to find a local supplier for this hose, or can contact the manufacturer Parker Hannifin. The replacement hose would be a 1/2" diameter Parker part number 601-8 or H017-8. To find a local distributor the Parker website can be accessed at Please wait while we redirect...
Use worm type hose clamps (use double clamps on each end) to attach the replacement hose to the existing pipe.
The locations of the flexible hoses are pictured below.
