2003 aviator check engine on why? car has brand

There is no way to know why that light is on without a Scan. There are hundreds of codes in the cars today especially with the luxury cars that have body control computers.

Try taking it to an Advance auto or Autozone. They will usually scan if for free and that will give you a place to begin to answer your question. The radio problem I believe is unrelated. In my years of experience I have not seen the radio make the CE light come on. The CE light relates only to safety or emissions.

Hope this helps. Get the code and post it and someone will help you figure it out.