A 2003 Toyota Tundra keyless entry remote must be programmed to your vehicle before it will work for you. Programming can only be done at a local automotive locksmith or dealership with the vehicle present. There are no onboard programming instructions available for 2003 Toyota Tundra remote. This keyless entry remote comes with brand new battery installed and is tested for functionality before sending. This Remote keyless entry comes with 3 buttons and if you look on the back of the unit, you may see some of these numbers: ELVATDD - 433 Mhz . Use these numbers to confirm that your Remote keyless entry will match this product and that it will work for your vehicle.