1996 GMC C2500 Fuel pump

My truck turns over but will not run. I know the fuel pump is not turning on when I turn the key on, but it is good as I changed it and found the old one is good also. I hook the fuel pump up directly to a battery and it runs and the truck will start and run fine. After is sits for a day or so I go back and the truck will not run again because the fuel pump is not turning on. It seams there is a switch that trips or safty feature keeping it from working, but if I bypass it and start the engine it will work for several days, (not hooked up directly, I un hook it from the direct wire) turning on and off the engine and then out of the blue the fuel pump stops working, and there is no power to the fuel pump as I have tested it at the tank. I understand there is no safty switch and there is a computer that tells the fuel pump to work or not. The error code is 102 MAF, Low flow, will this stop the fuel pump? Where is the reset button?
I already donated $10.00 ealier and though it was for this question, so I am only putting $1.00 on this one.