I know that this is an old thread, but for anyone who has experienced this problem, they know how frustrating it can be for the alarm (horn honking) and power door lock clicking to be going off, for no apparent reason, all hours of the day and night. I had this problem and had searched the internet for possible causes and found the answer on another forum. It was finally corrected by replacing the car's battery even though I wasn't experiencing any noticeable battery problems.