Anytime you disconnect power to the radio such as changing the battery, etc., it will require you to input the radio code. You will only have 3 attempts to enter the code correctly or it will lock you out. You can then try it again 24 hours later. Check your owners manual for the correct way to enter your code. Sometimes the car may have the wrong code card. If you find this to be the case after correctly inputting the code and it fails to restart your stereo go down to your local Acura dealership with proof of registration and they can look up your code on their computer and get you on the road again with tunes. They will not charge you for this service.