there would be a tiny printed circuit board holding the motor and possible the latch micro switch in the lock mechanism ,the CEM would be a partial printed circuit board containing the Field effect transistors and relays .
Try running ground from negative terminal of battery to pin 2 and 3 then latch the lock closed press tailgate open on switch and see if you get 12 volt on terminal 1 and that the lock opens . I would also check the loom where it enters the tailgate and the body for damaged or broken cables