We receive a ton of questions about programming remotes. We understand well what a confusing topic this is for the uninitiated in the world of automotive remote controls. That is why there is a whole section of information about programming on the Remotes Unlimited website. See it at the following link:
The most important thing to understand is that some systems are user programmable and some systems require a special electronics tool (commonly called a “Scan Tool”) that is not part of the typical home tool kit. For the latter systems, adding a new remote requires taking the vehicle and all remotes to be used with it to a vehicle dealership or a well-equipped automotive locksmith.
Note that I said some “systems” are user programmable, not that some “remotes” are user programmable. The programming method is a function of the system that is installed, not the replacement remote part. That is why the exact same keyfob may be user programmable on, say, a Chevy SUV and not programmable on a Chevy Express van.
One generalization is simple – virtually all aftermarket alarm systems are user programmable. For factory keyless entry systems, whether or not a system is user programmable and specifically how it is programmed to accept a new remote are both highly variable. That is why, if you are buying a replacement car or truck remote, you should also make sure you know the programming circumstances before buying the part.