I just purchased an '04 4Runner SR5 without the anti-theft alarm system option. I decided to forgo the $400 factory alarm system to save money, figuring that I would purchase an after-market alarm for about $200. After reading the manual, though, it occurred to me that the only difference between the anti-theft system that came with my truck (keyless remote entry and a panic button on the remote that sounds the horn when pressed) and the factory system is that it doesn't sound the horn if the doors are opened without the key.
Is there a cheaper way to enable this feature than purchasing a third party alarm? For example, is it simply a matter of installing a fuse that they've omitted?
Thanks, Darryl R.