ford cars are known are known for their door ajar switches sticking. The only way to tell without the ford tester would be to remove the door panel one door at a time for access to the ajar switch. They mount in the latch assembly and it is easier to remove the latch to get to, I have done them with latch in place(twisting and cuts usually needed) With the wds or the new vcm the ajar switches can be check without guessing. You might try spraying each latch assembly with penetration oil and then close, shut ,lock and unlock all the doors. There is a chance the GEM module is faulty but this would be the most common. let me know how it works out.