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Discussion Starter · #1 ·
Good evening all, having a weird issue...2016 LML with about 105k miles. Driving the other day and got "reduced power" message. Pulled over and cycled power with same results. Weird thing told me to try it in tow mode so turned it on and it ran fine until I got home. Hooked up bluetooth scanner and read codes P128E & P0088 (high fuel rail pressure) reset the codes and took it for a ride. Seemed fine, but when I stood on the gas it wouldn't go over about 2900 RPM then check engine light with reduced power mode, and change fuel filter message. Swapped out the filter and took it for a ride with scantool hooked up to read commanded and actual fuel pressure. Idles and runs great up to about 1800 RPM range, actual pressure shoots up over 30K then I get codes again for high pressure. repeated process several times with the same results.... Part throttle pressure spikes... full throttle 2900 max RPM.
Any ideas where to start? Pressure regulator??
Trying to avoid the dealership.
Any help is greatly appreciated, thank you in advance.

Don
 

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10,692 Posts
Sounds like fpr issue to me. Is the truck completely stock?
 

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10,692 Posts
If you pull the harness to the reg will it max out rail pressure? That will rule out the fpr and tell you if it's the cp4
 

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Discussion Starter · #5 ·
Didn't try that but pulled the reg. to check for debris an figuring it was the reg. I ordered the exergy "system saver" earlier in the week. No metal but a few small bits of debris. New reg installed and test drive shows all good, fuel pressure back to normal.
Seeing the dirt, I will be upgrading the filter and most likely adding a lift pump.
Thanks for the help.
 

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Glad you got it fixed
 

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if my fuel rail desired pressure is 5000psi+ and actual fuel rail pressure reading 1500 and less do i have a weak pump?
 

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10,692 Posts
4.5 4.6 at idle is normal. What is yours reading
 

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Whats it reading when cranking
 

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while cranking desired pressure works up 7000 and fuel rail sensor reads 145psi
 

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It needs around 2450 to fire injectors. Pull the reg and see if theres metal on the screen
 

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2013 C4500 Duramax LML Short Bus!
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what did you end up figuring out? THanks!
 
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