For many GM truck and SUV models, 2001 was a “split year” for factory keyless entry system remote transmitters. Models such as Chevy Blazer, Silverado, Suburban and Tahoe and GMC Sierra, Sonoma and Yukon all used two different keyless entry systems during the 2001 model year.
Vehicles assembled through February 2001 (“1st Design”) used 3-button or 4-button remotes with FCC ID KOBUT1BT on the back of the case. Vehicles built in March 2001 or later (“2nd Design”) used keyfobs with FCC ID KOBLEAR1XT. The keyfobs look very similar, so you have to be careful when buying a replacement remote. You should check the production date shown on the sticker inside your vehicle or the FCC ID on the back of your original remote to ensure that you get the correct replacement keyfob.
Buying the correct part is made more difficult by the fact that 4-button remotes with FCC IDs KOBUT1BT or KOBLEAR1XT are not all interchangeable. So, here are links to the correct remotes for GM trucks and SUVs in 2001:
Important Note: Not all 2001 GM trucks used remotes with these FCC ID numbers on them. Some vehicles still used an earlier design of keyless entry system used by GM in the late 1990s. For example, 2001 Chevy Express and GMC Savana vans, as well as 2001 Chevy Tracker all incorporated the older system, which used remotes with FCC ID ABO1502T.