2005 GMC Yukon "replacing relay heated seat 05" Questions

replacing a heating element in the front drivers side seat of 05 montecarlo SS remove the seat and you have to remove the bottom seat cover material but first check your power relays and wires to make

...relay or the fuel pump, or a vampire drain on the battery? I know the lights were off and nothing was left on. Pure SWAG on my part, but the only 2 things I can think of on the back cab wall are the ...