the back dor
As the name implies, it is the door which is on the right side of the car and the rear-most door, if there is more than one on that side.
The rear portion of a car is called the Hind Quarters.
Try opening a rear door then using the central locking button on the dashboard before exiting the car by the rear door
from the rear view mirror to the back of the car? or the rear view mirror to the front? as this does make a difference, also how close to the car where you?
were is the rear door relay switch located on a 2003 yukon
A person a can open the rear door from the inside. Get into the car from another door that will open and open it from the there.
replace the door or buy a new car.
Something is wrong with your rear door and it is not closing properly in the first place. Your door lock actuator is broken, it will need to be replaced.
The liftgate
The rear door panel is held in place by eight retaining clips into screws. Remove the screws near the door handle. Pry outward on each retaining clip. The rear door panel will come off.
You would firstly have to get a REALLY BIG door, as the sub will require the space for the bass.