2001 GMC SIERRA 2500 HD alarm horn stopped working, reg horn dose'nt work either. Alarm lights still go off when activated through key fob. Checked all fuses and wiring, driving lights not working either if thats related, can it be some sort of programing problem ,(wishfull thinking maybe !)thx Lawrance

After Market alarms are always full of issues especially when the batteries are disconnected of the car batteries are disconnected.

Find a Viper Alarms installer and take it in for reprogramming with their pro grade scan tool computer.

To arm content theft alarm.
1. Open the door.
2. Lock the door with the power door lock switch or
the remote keyless entry transmitter. The
SECURITY light should flash.
3. Close all doors. The SECURITY light should go off
after approximately 30 seconds. The alarm is not
armed until the SECURITY light goes off.

If a locked door is opened without the key or the remote keyless entry transmitter, the alarm will go off. The headlamps and parking lamps will flash for two minutes, and the horn will sound for 30 seconds, then will turn off to save the battery power.

I would start by replacing the FOB. Sounds to like the electronics inside it are bad. The only reason the horns would go off is if you hit the panic button. There is a slight chance the receiver is bad. But Fobs are cheaper to replace than the receivers. If you have two FOBs and they both react the same, then replace the receiver. Or just ditch the system. The keys (in the door locks) should still activate the alarm system.

You have 2 point of contact one is the alarm and the other is the horn switch itself, the horn switch is non op,

The alarm will time out and turn itself off after a minute or two when it is tripped. This turns off the alarm, not just the alarm horn.

Are you saying that you can't unlock a door from the inside by hand?

start the car. if that dose not work remove ground form battery then after it stops put ground back on that will reset the alarm.

red light? this is a factory alarm?? Is GM on the key fob? factory alarms dont have "motion sensors" and very few aftermarket alarms do. roll down the window and set the alarm, now open the door and see if it lights off.

the wiring on the steering wheel hooked up to the horn may have come undone or even around the steering colum there are two screws on the bottom of the coloum you can remove to acces the wiring, check to see if you may have a chaffed wire or even a cut wire

In order to 'RESET' burgular alarm, you MUST have the remote keless entry fob programmed for the vehicle - no other way unless you want to bypass/disable the burgular alarm relay and alarm horn. This, however, does not disable the 'flashers' when the alarm is activated. Bypassing the relay will allow you to start the engine, but you'll be driving around with your parking lights flashing.

Horn problem is either bad horns or failed clockspring behind steering wheel which is the connection for the airbag and horn buttons.