Arodrigues29

Hello all. Trucks a 2001 5spd/4x4. I had what seemed to be a failing lift pump so I installed a new FASS 150 and straw kit. My pump barely makes noise when I turn the key, sometimes my gauge goes to 2 or 3 psi other times 6 or 7. It seems like the pump is not getting the power it requires. I was told my ECM could be problematic. Truck seems to run fine I occasionally get a spike in my volt meter triggering "check gauges" but wouldn't that be a PCM issue? Any direction is greatly appreciated, I have searched but am nervous to shell out for am ECM if it's something else.