I have a Spare Key Problem

You can try another locksmith or, if you're sure the new key is a transponder key, try this. Start the engine with the working key. Shut off the engine and remove the working key. Now immediately insert the new key into the ignition lock and turn it to the run position. Don't try to start the engine!! Watch the security light on the dash. After a few seconds the security light should go out. When it does, turn the ignition lock back to the lock position but don't remove the key! Immediately start the engine with the new key! If the new key is a transponder key, this should work!! Leaving the key in the ignition for 10 or 30 minutes will not work. Disconnecting the battery will not work. If the procedure I outlined doesn't work, I'd take it to your local Chevrolet Dealer. Hope that helps! Jim

Thanks, gave it a try but the security light never goes out.

Then either the new key is not a transponder key or there's something else going on with the security system that needs to be fixed by your local Chevrolet Dealer. Sorry! Jim