Car Alarms: factory car alarm goes off when I use after market remote, starter car, car alarm

Question
I have a 2000 suburban.  I had a remote starter/car alarm installed right when I bought the car.  About a two years ago, for no apparent reason, whenever I unlock the car with the after-market alarm, the horn (factory alarm) goes off and starts to honk.  The only way to stop it is to start the car.  Then the problem went away for about a year, and now it's back.  Is there some way to permanently disable the factory car alarm?

Answer
Likely to be related to the PASSLOCK bypass installation.
Best idea is to go back to the installer for an evaluation
& repair. Without inspection, not telling exactly what
it would be without a first hand look.

Any reputable stereo / car alarm shop can handle
it if the original tech is not avail.

Good luck.

ALARMTEK