this morning i got into my truck 2 start it and the light come on and it was idleing up and down... ps i have a bad battery if that has anything to do with it

 

Low ignition voltage will cause an electronic throttle fault triggering Reduced Engine Power mode.

 

aloso what should my truck idle at rite now its at 400 or 450

 

my friend had a bad batttery or a connection was losse i cant remeber. anyways he had the same problem it was ideling low and had no power whatsoever. change your battery and that should fix it... should idle around 500 if im not mistaken.

 

Here's a 2004 4.8 idle table: