[abcd]

I have a Astra and the battery ran out in my key. The key still opens the door manually and starts the engine but does not work the central locking meaning I have to close driver door walk around car, open passenger door press central locking button close door (official instructions in user manual). Thank the lord I have a spare key meaning remote central locking is with me until the spare battery goes. How the heck do I reconfigure the key to work the remote central locking after replacing the battery?? (You would think the manual would cover it - just says go to your local dealership to be ripped off)