I think everyone should own and know how to use an OBDII reader. You can pick them up for $30 at auto store, or Amazon, you plug them into a plug under dash, it reads out a number. You hop on Google, and it tells you what is causing the code. (Places like Autozone do this for NO-Charge as well)
It just keeps you educated and your mechanic honest. Sometimes a code can mean a loose gas cap, what would your mechanic tell you?
I sometimes get the feeling, that especially the elderly and those with a motorhome, especially out of state, have a label on them that others take advantage of, and if you have one of these simple readers, just might help you display a tad of knowledge when you go to the shop.
Here is a link to a simple reader, there are more sophisticated ones for sure. They even have them that you plug in, leave plugged in, and use an app on your phone. https://www.amazon.com/OBD2-Scanner-OBDII-Code-Reader/dp/B0743X5WV8/ref=sr_1_12?s=automotive&ie=UTF8&qid=1531311604&sr=1-12&keywords=obd+reader
Sorry if I hijacked the thread, maybe the OP has a system onboard to do this, but hoping others read the thread and consider owning a little tool like this.