I need some help majorly i have a 04 Tahoe 2wd with a 5.3 and for the past month and half it will not start whatso ever it doesn't like to stay running if it actually wanted to crank i have grounded out some wires around the top of the motor to see if a ground came lose or something first was going to replace the fuel pump but you can hear fuel pump cutting on and cut back off and it will crank sometimes so I then put another throttle body on there from another running truck and after that it would still try and crank but wouldn't i have no idea what to check or even look for. TIA all the help the better I thank you

 

Welcome from Florida. Just because you can hear the fuel pump running, that doesn't mean it is producing enough pressure. You can do a fuel pressure check or spray starter fluid into the throttle body and if it starts right up and runs for a few seconds, you probably have a bad fuel pu8mp.