This may be a little late to help but my 1998 STS had a similar problem in that the alarm would go off when I tried to lock the car with the key. Flashing lights horn wakes up the cows and the dog and it all gets really loud . A simple reset of the ecm fixed the problem ,by diconnecting the battery for about 20 minutes with the lights switched on the drain any residual power to the computer-ecm it resets to default and everything worked great , for a while anyway a couple years later had to reset again. but for the most part it was fine till i got rid of the car. Hope this helps