2003 Chevrolet Trailblazer Remote Programming Procedure:
IMPORTANT: Before initiating remote programming mode, have in-hand all remote you want to use on the vehicle, including old ones you want to keep working. Once you program the remote, all previous codes will be removed from the memory. The other remotes will not be functional until you program the transmitters again.
1. Close all car doors, all windows closed, wait for dome light to turn off.
2. Insert the key into the ignition.
3. Hold down the power UNLOCK button on the driver’s door panel-continue to hold down until instructed to release in step 9.
4. Perform steps 5-8 quickly.
5. Move the ignition switch to the ON position (as far as you can go WITHOUT cranking the engine).
6. Rotate the ignition switch to the OFF position.
7. Rotate the ignition switch to the ON position.
8. Flip the ignition switch to the OFF position.
9. Release the power unlock button on the door panel. The vehicle will lock and unlock the doors automatically.
10. Hold down the LOCK and UNLOCK buttons on the transmitter as well until the door locks lock and unlock. This step may take up to 30 seconds.
11. Repeat step 10 for each additional fob(including any existing keyfobs).
12. Flip the ignition switch to the ON position in order to get out of the fob learning method.