Well, as you surely know, there is no "one thing" that sets the CEL. All depends on the code.

While it is easy to draw a conclusion that nobody's issues are getting fixed, that is not true. Even my lemon was ultimately fixed....

We are getting ahead of ourselves, but I suspect the fix will be to replace either EGR or temp sensors, and do some reprogramming.

Make sure you ask (and receive) the codes set in the DDE memory. I force the SA to write 'read and save codes, provide to Customer'....

One thing I will caution- some shops, as a matter of practice, reset the codes and THEN see what returns...often you get "we didn't find anything wrong", (Arguably, this is not a bad strategy if you are out of warranty and only want to repair issues that are 'hard failures', with constant errors.) Make sure you have a short chat with the SA that you want whatever code that was tripped to be recorded.

GL

A