The switch in the back door will get seized with age. When this happens the latch assembly will stay stuck halfway open and closed allowing you to close the door. when the door locks the latch will jam. and now will not be able to open until the latch is freed up and unseized again. you will have to access the latch by going through the inside and popping the panel away from the door. then using a screw driver force the latch to the fully closed position. then unlock door and open. Lubricate the old latch till it moves freely. then it should work properly for you.. good luck

Does the latch energize? Or is there no power at the motor for the latch?

I suggest to check this wiring diagram... to me, sounds like the mechanism in the motor drive for the lid release is bad. The motor is energized and working. Here is a link wiring diagram for zooming...



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