From your description it is dealer installed security. You may take a look at your paperwork they gave you when you bought it. It will be listed, not on the factory window sheet, but in the extras you paid for. You can also call the dealer, but don't expect them to be much help. They buy these systems for very little, have some quarter trained kid install them, then charge you big bucks for them.
If you can find the name, you can get the programing information.
If you are VERY lucky, they put in a Powercode.
I suspect it is a much cheaper unit, mounted under the column, behind the kick panel. Hopefully it will have an adjustment. You could probably take it to the dealer and they might be able to adjust it. You may find they had it done at a local stereo/alarm shop.