LMM fuel problem?

12vf250

12vf250

I wear my bill curved
Hey guys, Im not real familiar with Dmax trucks, so I need a little help. Had a customer tow a truck to me on Friday that would only idle, and was in reduced power mode. To make a long story short, it had a boatload of DPF codes in it because it was plugged. I pulled it off, and the truck runs better, but on a test drive it is setting a P0087 FRP too low code. Changed out the filter and cleared the codes, and the truck ran great for half a block before the change fuel filter message came up on the display, and the engine derated again. WTF!? I watched the fuel rail psi with my scan tool, and its not dropping. Im lost on this one. What else should I be looking for? I have ordered a tuner for the DPF delete. Is there any correlation between the DPF being mia and the FRP code? Thanks in advance.
 
hate to be the bearer of bad news, but if it came to you in full limp w/ catalyst full, you're going to have to put the exhaust back on, tune it back to stock, and let it go through a regen cycle in order to come out of limp.

been down this road a couple times... once they're in limp on a clogged dpf fault, there is NO WAY to get them out short of a new tuned ECM or putting the exhaust back on and letting it get through a regen cycle

I keep an LMM exhaust system with sensors/etc. on hand for just such an occasion

I would say "have fun with it", but I already know you're not :(

<-- hates LMM's
 
Forrest Nearing said:
hate to be the bearer of bad news, but if it came to you in full limp w/ catalyst full, you're going to have to put the exhaust back on, tune it back to stock, and let it go through a regen cycle in order to come out of limp.

been down this road a couple times... once they're in limp on a clogged dpf fault, there is NO WAY to get them out short of a new tuned ECM or putting the exhaust back on and letting it get through a regen cycle

I keep an LMM exhaust system with sensors/etc. on hand for just such an occasion

I would say "have fun with it", but I already know you're not :(

<-- hates LMM's
Click to expand...

Would they still throw 0087 codes though? You have do a forced regen with a tech II? He did say it came out of limp mode until it threw the 0087.
 
Thanks for the ideas guys. I dont have the truck at the shop right now, but I will get it back in a couple days. I ran it through a DPF replacement with my Snap-on Modis and it came out of limp mode until it through the P0087, so its definitely the fuel problem thats causing it to derate. Its throwing DPF codes too, and thats why I ordered the tuner, to shut off the regen cycles. The thing that is weird is that I have graphed the FRP and its not dropping at all. Is there some sort of fuel restriction sensor on the supply side that would cause this code? Also, the fuel tank was almost empty when it was here, so I took a sample before I filled it up with fresh fuel. The fuel that was in it looked good, and the filter I took off looked clean.
 
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It is probably comparing actual FCA current to desired for X fuel flow inside the ECM, and seeing the actual current is going outside the desired range and setting the P0087 code. This is how it calculates fuel filter percentage, and when it sees a rapid drop it will trigger the P0087 code. Check the fuel lines by teh trans and tank for kinks, and also teh fuel pickup for obstructions. A vacuum tester hooked up to the test port would take all the guesswork out of it though.
 
Well, I never got the truck back to have a second look at it. But I did learn some things about how these trucks work. Thanks for the help folks.
 
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