3 door does NOT HAVE MOTOR, it uses a solenoid, ie electrical plunger, same as xr4i.
I would firstr asscertain that you are getting a LOCK PULSE as they are succeptible to broken wires in tailgate, due to constant flexing opening and closin.
The solenoid looks like a drum about 1 1/2" in diametre and about 3/4" long with a little rod about 3/4 inches long attaching to the lock area, the solenoid is held onto a flat plate by boot lock, secured by the LARGE FLAT golden colour screws near lock.
tabetha