I just bought my brother-in-law's 06 mustang. He had the dealer install the Ford, OEM active security system. He bought the car brand new and had no issues for two years until the battery leaked and died which caused the module card in the alarm to die and be subsequently replaced.

My brother-in-law drove the car exclusively in Arizona and while I was in Arizona the alarm worked perfectly; however, the day after I drove it home to Utah, the alarm went off immediately after I activated it by pressing the lock button twice. After some experimentation, I discovered that the alarm goes off immediately if the car activates it too, i.e. if I press the lock button once...the alarm goes off after 10 seconds. If I lock the car manually, the alarm goes off after ten seconds.

After reading a post about a faulty hood latch sensor activating the active alarm I inspected the hood sensor but found no corrosion. I attempted to examine the other truck/door sensors but discovered nothing obviously wrong.

I suspect the the issue involves the Interior Theft sensors (IT-s) because after the alarms goes off, I deactivate it and push the override button, the horn beeps once which, according to the manual, means the interior theft sensor caused the alarm to go off.

I thought that I had fixed the problem by following the instructions in the manual for decreasing the IT-s sensitivity; however, when I lock the car and the alarm activates now, the horn beeps 4 times, then randomly over the next few minutes. When I come back to the car after work the horn is not beeping (I think) but unlocking the car causes four beeps indicating that the alarm has been tripped. Override button again indicates IT-s as the culprit.

I have not been able to reach 1-800-FORD-KEY for assistance. Any help you can offer is greatly appreciated.

Has anyone else had this much difficulty with the OEM active alarm?