Security system

Hello, This is very common. There is a pigtail on top of the lock cylinder (under the plastic cover) that gets a bad connection all the time. Check it, see if you have corrosion, bad wires, a broken pin, or it feels loose. Of course, the key could also be the culprit, and replacing/reprogramming the key is much easier. All that said, the last thing I want to do is have you chasing through the dark to figure this out, so I do recommend having professional diagnostic scanner connected to monitor the system at initial starting. That would shed light on the issue.