I found this info on the forum. I'm gonna try this seems like a good start
Found a Fix for P0087, P0093 when under a load
My original thread with the full story of the problem was posted a couple weeks ago under "P0087 when under load going up mountains".
I FOUND A FIX FOR THE PROBLEM-COST ME $50 IN PARTS, LESS THAN AN HOUR OF MY OWN TIME, AND $30 FOR A TECHS ANSWER ON Ask Question & Experts Answer You ASAP! Name Your Price, Get Online Answers & Help - Just Answer!!!!!!! GM BULLETIN #PIP4526!!! Go to a GM dealer and ask them to print out this bulletin for you and do the repair. I had to order the hose (special kind) from a distributor of the supplier listed in the bulletin-$6 a foot x 3 ft (more than enough) + shipping, use standard hose clamps from a local autoparts store-2 clamps on each end of the hose.
When my husband got under the truck and looked at the section down by the tranny there were 2 spots in this 1.5 ft area that were soft and collapsed, replaced the section per the bulleting last night, went thru Jellico Mountain today with a camper like usual and the code DIDNT set.
What happens is after the hose gets good and hot (4-6 hrs driving), it softens and then collapses when you put the truck under pressure with a load---this cannot be duplicated in a shop with any testing due to special circumstances---unless someone is gonna hang underneath your truck while you drive down the road and watch to see if it collapses (LOL), which is why no one can figure out this problem. The $50 for the parts is worth the try...worked for us.
If anyone has any questions you can email me at "email@example.com"...I will be more than happy to help. I would like to thank Hal at Eisinger Chevrolet in Columbia Falls, Montana for leading me to this bulletin for the fix!!!
(this bulletin actually has pictures of where the hose sections are located but they wouldnt transfer onto here, so have a GM dealer print it out for you)
#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
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
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.
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.
2009 Chevrolet Silverado 2500 HD
LMM, Allison Stock
AMSOIL bypass oil system