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Discussion Starter · #1 ·
I have a 2007 lbz. At idle my frp is perfect and when I elevate rpm in park but when I'm driving down the road and go past 3/4 throttle my frp is around 40psi lower than idle and it ends up setting a low fuel rail pressure code and sending the truck into limp mode. I have replaced fuel filter and the 2 soft lines coming in and out of it, the valve for the pressure check stem. And the soft line coming from the tank on the driver side. I have no fuel leak that i have noticed and I have had no luck so far with fixing the issue or even getting close. I am stumped. UPDATE: replaced cp3. Ran good for about 3 days before going back into limp mode with no throttle response this time. Went back in and replaced fpr, after replacing, the truck would crank but not start. So i went back in once agian anf replace both cp3 and fpr this time. Put it back together and its still saying it has 0 rail pressure. I have no clue what to do next
 

· Former GM Tech and parts
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Need to see what the injectors are returning. I wouldn’t think they would be returning that much, put it’s possible. Need to see what the vacuum is reading at the vacuum port to see if the cp3 is pulling enough vacuum which it should be since it’s new. See what you get from those and isolate from there.
 
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