We have a 2000 Expedition. Whether running or sitting with no key, the locks keep locking. Sporadically, they keep trying to lock, even though they’re already locked. Also the interior dome light comes on for no reason. We’ve bought a new battery, but that didn’t help.
In normal operation, do the doors automatically lock when you close the driver’s door? If so, I suspect a faulty door switch.
The problem might be with water leaking past the windshield onto the Generic Electronic Module or GEM, and or the fuse box. The GEM is mounted above the fuse box. I’ve seen this happen on two Ford truck based vehicles.
If the GEM or fuse box gets wet, it can cause all sorts of wierd electrical problems.
We had disarmed the auto locks years ago. We tried the procedure again to no avail. Now the doors lock when the car is put into gear as well as any other time of day or night.