When set, the intrusion alarm goes off during the day, without any actual disturbance or intrusion. During the night, the alarm system is normal, and is not 'mysteriously' activated. The sun is shining here in Dallas during the day, so the problem may in fact be temperature related. .... Could this problem be related to something like a fuse or some connection which has developed oxidation? Maybe someone else has run into a situation that is similar to mine .
Thanks for any tips.
Dave

 

is this a stock alarm

 

Yes. I think it is called SecuriKey+. ... It came installed with the car, and is controlled by a RF transmitter on the ignition key. ... Sometimes the horn will sound in even bursts for about a minute. Other times there will be a very rapid sequence of 5 short horn bursts. Sometimes the event will be during the day, but it also occurs during the night. I checked the battery voltage and it is 12.6 or so. A battery load tester showed that the battery was a little on the weak side, but not extremely weak. I think I will remove the glove compartment box tomorrow and see if removing the alarm circuit fuse, #25 I think, and cleaning it will produce any difference in symptoms.

 

It might/could be the brain or CPU have gotten fried from heat..

 

The actual problem turned out to be an adjustment of the alarm sensitivity. I had to take the car to the local dealer to have this done ... $100+. Apparently, this was something that could not be done at home, requiring a computer hook-up. ... On the positive side, the dealer inspected the car and alerted me to a water pump leak, and also that the timing belt should be replaced.

Dave