I had a battery replaced a few days ago in my 2001 Honda Accord and now
 

my radio system is asking for a code?

This is an antitheft system on Hondas. Any time the radio loses power to it (ie: unhooking the battery) the radio asks for a code. This is done so that thieves cannot steal your radio and plug it into another car. Hopefully you have the code somewhere. If you bought the car new, it was delivered to you with your manual. If it was a used car, check the glove box. What your looking for is a credit card sized plastic card with 'Radio Code' and the code printed on it. This card also comes with code 'stickers' and if you bought the car used, someone may have stuck one of these in the maual or the glove compartment. Check for that too.If you can't find the code anywhere you need to go to a Honda dealer. Hopefully they can look up your code by VIN, but they may have to remove the radio to get at the serial #.Good Luck!!

when power is cut to the radio, the radio goes into lock mode. someone steals your radio it wont work without the code. check your owners book for the code .

I had the same problem last year. Since I bought the car used, the dealer did not have the code. I got lucky; the dealer was willing to contact the original dealership and get the code. If you can't do this, then you will need to take the car to a Honda dealership and have the service department pull the radio. They can then submit the serial number to Honda and get the code. It's very simple (for them). They get this a lot, so you won't have any explaining to do. Good luck!