disconnected the battery for matinence and now radio will not function, when powered on none of the buttons respond and when preset buttons are pressed displays a code then error message. any honda guru out there help me fix this hopefully simple problem

 

Is this an aftermarket or stock radio?

 

There might sometimes be a lock code to unlock the radio for use. It's just in case someone rips your radio out so they can't use it. Some radios have it some don't