Where do I find complete access codes ?

What is your question?

I have found several apps for my phone for answers to codes. My problem is I don't have the complete code. I get generic answers that seem to confirm what I think is wrong but I want more information and I need to know what are (P,U,B, and C) codes? I miss the good old days when all you had to do was listen to your car. My engine is a 318---V8