2009 GMC HD3500 loss of power issue after full throotle

[Supermoto68]

Full exhaust system, airfilter, and Mini Maxx tuner. Overall run just fine except on interstate if I go full throttle engine light comes on engine goes into limp mode. I use mini maxx tuner to run diag and get a code that says fuel pressure issue, clear it and power comes on right away. Why is it doing this and how do I fix it.

 

[2004LB7]

Most likely low fuel pressure. The ECM is asking the pump to make x amount of pressure but it's not achieving it.

Several causes for your situation. Fuel filter is plugged up and restricting the fuel to the CP3 pump. Air getting into the fuel causing the pump to under perform, common for the filter housing/head to leak. A collapsed or kinked fuel hose or possibly you have a weak CP3 pump.

A lift pump can help with keeping the air out of the fuel and boost a weak CP3 pump a little. Start with the easy stuff like replacing the filter and using a clear hose after the filter to see if you have air in the lines, if so you may want to rebuild the filter housing or replace it. Replace any fuel lines that looks degraded or old. After ruling out everything else then start looking at a new CP3.

How many miles on the truck?

 

[PDWolff]

I second the lift pump. I also have an 09 LMM and it would defuel on tunes 3,4 and 5. Put the lift pump on and a factory fuel filter delete housing and I haven't had any fueling problems since.

 

[NC-smokinlmm]

Just put a lift pump on it and go on with it…