I have a 2005 GMC Yukon won't crank

Check battery voltage when it won't crank. If it's around 12 volts then move to checking the starter for battery voltage. It should also be around 12 volts. This could also be an ignition or security system issue but that will require a hands-on inspection by a qualified technician. Use this link to find a good shop near you. https://repairpal.com/repair-shops Alex

Try cranking engine with transmission in neutral - park / neutral switch's are problematic. Wiggling shifter up / down just a bit while in neutral may help.