I've had my 99 Durango SLT for over 4 years now, and I remember when I first got it, the alarm remote was working fine.

Now, when I push it to arm, it will lock the doors, but the alarm won't arm.

When I push unlock, it will unlock the doors, but I won't hear the horn notification.

It's been awhile, but since I have it on my mind, I'm just throwing it on the forum before I forget again.

 

It could be that your ctm(central timer module) is not working. I had mine replaced and it did fix some security issues. But I am not a mechanic, just a thought.

 

My 2000 Durango does not sound the horn when you unlock the doors with the remote. It only sounds the horn when you go to lock mode and the security system is enabled when in lock mode.