If you are buying a replacement car remote, searching by the FCC ID can be a very useful starting point. Most car and truck remote transmitters show the FCC ID of the part on the case. This is true whether the transmitter is a stand-alone keyfob or is integrated with a key.
Some remotes are unique to an FCC ID; that is, there is only one style of part that has that particular FCC ID on it. For these, if you match the FCC ID of your original part there should be no question that the replacement remote is the correct part.
You have to be a little bit cautious with web searches though, because search engines often return close matches, not just exact matches, for what you search. This pitfall can be made worse by the unscrupulous, or just plain dumb, practice of some remote web sellers, who list an FCC ID to capture web traffic even though they do not sell that part and may not even know what it is.
Another pitfall to be aware of is that, in many cases, there is more than one part that has the same FCC ID. When this is true, you cannot be certain that parts are compatible (interchangeable) just because they have the same FCC ID.
And, just to make your life (and ours) a little more difficult, many parts manufacturers assign FCC IDs that only vary by a single character or digit. For instance, Lear, who is a major contractor to the auto companies for keyless entry systems, created one family of remote transmitters with FCC ID KOBDT04A and another with FCC ID KOBGT04A. To make matters worse, both of these FCC IDs include many parts that are not interchangeable.
As, an aside, remotes with the “D” in the middle of the FCC ID were used on Dodge and other Chrysler-made vehicles, while remotes with a “G” in the middle were used on keyfobs for GM keyless entry systems. (We are not sure if this was intentional or happenstance.)