For me the button only works when you power down the car. (When the engine's running, turn it to the accesory position, meaning the engine's not running, but the car is still on.) Now hit the code button. Then you use the four buttons to set your code. 1000 adjusts the 1000 position, 100 the 100 position, 10 for 10 and 1 for 1. Once your code is displayed, you hit the set key. Now turn the car off. The code button should now have an LED on. (Note: This is a good "fake alarm" blinker.) When you turn the car on, you have to leave it in the accesory position, hit the code button, type in your code, then hit set. If it works, then you can start your car. If it doesn't, you have two more trys before the starter kills itself for 24 hours. (There are ways around that, though.) Good luck. --Seth