2004 Chevy Avalanche Remote

Here's how to do the remotes, but as for the remote start I have not seen replacing a vehicle battery wipe those out! You need to find the maker of the remote start and get the info from them, most will reset by turning the key on and get 10 feet from the truck and press and hold 1 or 2 buttons down ffor about 10 seconds.
Method 1 - No Tools Required, Program All Transmitters 1. Close all the vehicle doors. 2. Insert the ignition key into the ignition lock cylinder. 3. Press and hold the door unlock switch. 4. While holding the door lock switch in the unlock position, cycle the ignition ON, OFF, ON, OFF. 5. Release the door unlock switch. The doors will lock and unlock to confirm the program mode. 6. Press and hold the LOCK button and the UNLOCK button simultaneously on one transmitter. After a delay of approximately 15 seconds, the doors will lock and unlock to confirm the programming of that transmitter. 7. Repeat the previous step to program up to 4 transmitters. 8. Turn the ignition switch to the RUN position in order to exit the keyless entry transmitter programming mode. 9. Operate the transmitter functions in order to verify correct system operation. IMPORTANT: All transmitters which are to be recognized by the PDM must be programmed in a single programming sequence. When using this program method, all previously programmed transmitters will be erased upon the receipt of the programming signal from the first transmitter. The order in which the transmitters are programmed will determine its numbering position within the PDM memory. The first transmitter programmed will be transmitter #1, and the second transmitter programmed will be transmitter #2. The number stamped on the transmitter case is for reference only; #2 can be programmed as #1, or vice versa. Additional unnumbered transmitters are also available.