2004 Chevrolet Trailblazer Remote Programming Procedure:
WARNING: Before beginning programming mode, have with you all keyfob you will be using on the vehicle, including old ones you want to keep working. When you program the fob, all previous codes will be deleted from the memory. The other transmitters will not be functional until you program the remotes again.
1. Shut all vehicle doors, all windows closed, wait for dome light to go off.
2. Insert the key into the ignition.
3. Press and Hold the power UNLOCK button on the driver’s door panel-do not release until step 9.
4. Perform steps 5 through 8 in fairly rapid succession.
5. Flip the ignition switch to the ON position (as far as you can go WITHOUT starting the engine).
6. Rotate the ignition switch to the OFF position.
7. Flip the ignition switch to the ON position.
8. Rotate the ignition switch to the OFF position.
9. Let go of the power unlock button on the door panel. The vehicle will lock and unlock the doors by itself.
10. Hold down the LOCK and UNLOCK buttons on the transmitter as well until the door locks cycle. This step may take up to Half a minute.
11. Repeat step 10 for each additional keyfob(including any existing keyfobs).
12. Move the ignition switch to the ON position in order to exit the transmitter programming function.