I have 2013 Honda CRV with Panasonic radio/CD. On the radio only not the CD I hear a faint pup pup sound, most noticeable over quiet music or in the pauses in speech, whether engine on or off.

SOURCE: Radio code for Honda CRV 1999

If the radio has not been changed in the past, then I am almost certain that your local Honda dealaship can help but as always they may charge you. There are auto centres that are equipt to change the radio code and they do charge.

SOURCE: honda crv engine light

I would go to your local Honda dealership and tell them the engine light came on. They will hook it up to a special computer and they will be able to tell you why the engine light came on and what's wrong with the car. Not sure what the cost will be to get it checked out. If you don't have the money for that right now.

SOURCE: 2002 HONDA CRV COLD ANTIFREEZE LEAK

this happens alot on older vehicles most often times because the coolant hose shrink and expand around a fitting. try and tighten all coolant clamps. this often is all it takes to solve the problem. you should also look to see that all seals around heads of engine show no seepage

SOURCE: 2002 Honda CRV factory radio - CD Plays but will not eject

mustangs do the same thing, on those if you swipe a credit card UNDER the cd while its ejecting it will come out, hope that helps.....

SOURCE: MY 2007 HONDA CRV CAR RADIO LOCKED AND IS ASKING FOR CODE

inside glove box there should be a sticker with the radio serial number and code. if that has been removed then you could try the honda owners site. you'll need the vin # and some other info
I was able to get the code recently for my 2010 CR-V