If your car battery goes dead, the memory of the car's computer will be deleted. With it will go previously programmed authorization of your keyless-start proximity sensor, or smart key. To get the computer to recognize your smart key's signal again, you'll need to reprogram it. A common anti-theft feature across car brands is that entering programming mode erases all previous smart key authorizations. What this means for you is that all smart keys that you want to work in the future have to be programmed in the same session, whether they used to work or not. Preferably, you will program the computer yourself, since a dealership would charge you upward of $100 per smart key. Unfortunately, no small number of instructions programs most car makes' smart keys. Chevrolet by itself has no fewer than 15 sets of instructions for its vehicles--none of them interchangeable.
Find your own car manual for programming instructions. If they aren't there, proceed to Step 3. If you've lost the manual, proceed to Step 2.2
Find your lost manual at diplodocs.com or ownersmanualsource.com. Both websites are free. The latter is for cars specifically. The former provides a link to your car's manual as an icon in the upper right portion of the page. Several pay sites will sell you a new manual, but they can cost as much as the price of having your smart key reprogrammed at a dealership, which defeats the purpose.3
Find programming instructions at keylessride.com or programyourremote.com. The former is a pay site while the latter is free. If your own model-year combination isn't at programyourremote.com, a similar model's instructions may work. Otherwise, go to Step 4.4
Call a dealership asking for programming instructions over the phone. Some dealerships may be less cooperative than others, viewing you instead as a source of income if you come in the store for a programming. So you may have to call several dealerships to get free instructions.