This is made for users without any experience with car radio !!! Brand new models are locked with several options ,anti theft ,Immo protection ,can-bus protection ,code locked and may be some more that I still not know! If you ,do not know which kind of protection your car radio have ,do not disconnect it from battery even if it is flat before ask somebody with experience! 1. Today many models can be bring back to life just with reading all numbers and text from sticker to your nearist Dealer of your car ! 2. If battery is changed radio can ask for CODE! Please do not input any if you are not shore that you have supplier CODE! 3. If you bought secondhand car and radio not respond ,or shows some message like lock 13 ,code, safe ,or beeping ,please refer to your nearist local decoder ,they always have fair prices for your units ! Other way you will lose lot of time ,in most case lock out your radio ,and than decoder will charge you extra to unlock your radio from that state and give you correct code ! Another way you can bring dead your radio and ,pay for that almost as for new radio !!! 4. If you wanna solve it alone than you will must to have some electronics skills. 5. This is intended to help all people ,all of kind ,just by the rules ,because here are users who are Prof. I hope this will open eyes to all who search for quick and free of charge solutions here !