I recently had a Viper 5701 alarm system installed in my 2009 GMC Sierra truck. Afterwards, I noticed that even when I try to arm the system silently, the truck horn still honks once. The installing dealer basically said there is nothing he can do as far as making the Viper system silence the truck horn. Frankly, I think this is BS since I paid for a GM Interface module that I would have thought would have taken care of all related systems. My Viper system still flashes the lights, turns on (and off) the dome light and does just about everything else that the old key fob did as far as locking and unlocking the truck. I might add that I am aware that on my old key fob that pushing the lock button only once did just lock the doors without the horn honk. If I wanted the horn to honk, I had to press and hold button down until the horn honked. I may have stumbled on the solution however. Between reading my manual, talking to the service manager at a GM dealership, and reading on this forum I learned about the DIC switch (that wasn't present on my vehicle, like most are not). I have ordered the switch and should have it in just another day or so. Through the DIC, I am supposed to be able to "program" the door lock configuration and turn the horn off. BTW...apparently these cannot be accessed using the TECH-2 service computer. The service manager tried, but admitted that he had no experience doing this with the TECH-2. He did take a look and said that he could not access the correct module. I am just posting this here to see if anyone else has experienced the same thing when installing an after-market alarm system, whether it was a Viper system or some other brand.