Hi, if you need to change the battery at the key then the codes are gone, but no problem, here the description how you can re-learn the / the keys. Always take the second key inside the car so that it is programmed with, simply put it in the center console. Well done. Greeting Master66 ————————————————————————————– 1. All doors are closed and unlocked. 2. Ignition key in Z 3. 4 times at the switch at the driver’s door “unlock” and “lock”. (on – too, on – too, on – too, on – too) 4. 4 x ignition key from ignition lock pull off and use (out – in, out – out – in, out – out – out – in) 5. Start the engine and run about 5 seconds, then let ignition off. (keys can be stuck!) The doors unlock 1 x automatically. 6. 1 x “lock” at the hand transmitter. [doors are automatically pressed 1 x open and unlocked! In addition, the warning number beeps a few times. (If unlocked and unlocked, but it does not beep, in most cases the Key Free ECU or the backup for it is defective.)] 7. Detach key, done.