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I've picked my injector plugs at least 10 times, re wrapped my ficm harness, changed the fuel filter twice, and nothing limp mode. Im pulling codes p1093 and 1094. Can someone help? :(I im limping to work. Will prolonged driving in limp mode hurt? Thanks guys.
 

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You should do this test first--

At the rear of the driver's fuel rail, there is a "U" shaped hose-- remove the hose from the rail fitting, and plug the hose. Attach a long hose to the rail fitting and put the end in a bottle. Now drive the vehicle hard-- if you have fuel in the bottle, the FPRV is bleeding off rail pressure. You need to shim the valve, or replace with a race valve [plug] that will not bleed pressure.
 

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I did the shim kit and must say its fairly simple. took me an hour and a half. Truck runs fine now! Its security so yeah do it guys!! 20 buck and a hour n a half work is easy!!
 

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Do the LB7's use the same FPRV setup as the LLY's, if so does this test apply to the LB7's?
 

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So u plug the end that goes to the tank and attach another hose to the rail and into a bottle? Sorry for the confusion thanks!
 

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Yes, you want to measure the fuel coming out of the back of the fuel rail. That is the nipple at the back if the driver's rail, where the "U" hose is attached.
 

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I did the shim kit and must say its fairly simple. took me an hour and a half. Truck runs fine now! Its security so yeah do it guys!! 20 buck and a hour n a half work is easy!!
Glad to here you got it fixed, it is a common problem on the LLY along with the FICM harness. :thumb
 

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I just replaced my fuel pressure relief valve figured it would take care of it and nope! Then changed fuel filter today and still same thing... goes into limp after cruising down the road at 70 after 5-7 minutes 2000 rpms and thats it any suggestions
 

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I just replaced my fuel pressure relief valve figured it would take care of it and nope! Then changed fuel filter today and still same thing... goes into limp after cruising down the road at 70 after 5-7 minutes 2000 rpms and thats it any suggestions
do you show any codes? welcome to the site
 

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subscribed.
 

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Glad to here you got it fixed, it is a common problem on the LLY along with the FICM harness. :thumb
That FICM harness, isn't it an expensive part? I believe that's what went out on my truck recently. I was doing bout 73 down I-40 and the truck lost power, engine light came on. I pulled over and the truck was running rough as all get out. I turned it off, let it sit for a min, and then started it n it ran fine. I got up to 55 and all seemed well, cranked it up to 65 and same thing happened. It got to the point that it wouldn't even try to rev up when I pushed the pedal. $611 to get it fixed at dealer cuz my dad's mechanic couldn't figure it out.
 

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I know the FICM its self is expensive, around $500 here in Canada. But the fix is cheap. Cut the zip tie holding the harness to the alternator support. Open up the tape and closely inspect it for bare wires. Repair them if you find any, you have to look very closely. Then get a piece of heater hose and put it around the harness where it came in contact with the alternator bracket. I just left mine loss, didn't zip it back down to the bracket.
 

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do you show any codes? welcome to the site
yes its throwing p1093 now which i believe is low fuel rail pressure? Not sure what to do next was told to replace fuel pressure reg... any thoughts?
 
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