Well what happened is the anti teft engaged on the radio when you unplugged the battery. To get the code for your radio you have to get the serial number for the radio and then call any local honda dealer and tell them your serial number they will look it up on honda in. then give you the code witch you put in using the preset station buttons on your radio. to get the serial number for the radio you have one of three ways to choose from 1st look inside your glove box along the back of it and along the sides you should see a small white rectangular sticker with black numbers and or letters on it that is your serial number. 2nd. if you do not have the sticker in your glove box with the serial number then you have to pull the radio out of the dash and get the serial number off the back of the radio. 3rd. You can take you car into any honda dealership and they can pull the radio out for you then get your radio code but they will also charge you and hour for labor witch is 82 dollars.In the futer to prevent this from happening you have to plug a memory saver into your pcm port before you unplug the battery if you dont you will have to input the code for your radio every time you change the battery but your best option is to have a honda dealership change you battery the next time you need one because the memory saver for the pcm is not something that you can get ahold of very easily