My battery died on me and I had the old one unplugged for like a day before installing the new one. All is well with the car but when I turn on the stereo it says Code on the display. when I press buttons it says Err1.. 2.. 3.. and it goes up as I press different buttons. Yes it's the stock HU. Will I have to take this to Honda to fix or what? Thanks!

 

This is an "anti-theft" feature of the stock HU. Whenever the power is interupted, you must input the "code" to get it to work again. You should have this code in a plasticized card with your owner's manual. If you don't have the code, you'll need to go to the dealer, prove that it's your car and HU and pay them to unlock it for you.