2005 Chevrolet Trailblazer Remote Programming Procedure:
NOTE: Before entering remote programming mode, hold all of the transmitter you want to use on the vehicle, including old ones you want to keep working. Once you program the keyfob, all previous codes will be taken out from the memory. The other remotes will not be functional until you program the keyfobs again.
1. Shut all vehicle doors, windows closed, wait for dome light to turn off.
2. Put key in ignition.
3. Press and Hold the power UNLOCK button on the driver’s door panel-don't let go until 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. Switch the ignition switch to the ON position.
8. Move 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 all at once until the door locks lock and unlock. This step may take up to Half a minute.
11. Repeat step 10 for each and every additional keyfob(including any existing fobs).
12. Switch the ignition switch to the ON position in order to quit the keyfob learning function.