Secondly, don't worry about offending, I'm very thick skinned!!!
I've been a mechanic for over 30 years! I don't confess to know it all, and never will. I believe in learning something new everyday; and have a full understanding of the common real system.
One of the scan tools I am using is the snap-on, Verus, this gives me most of what I need.
I suppose I was being lazy, writing into this forum, looking for a "common fault"!! I kept my description short, brief and to the point so as not to bore anyone when reading!!!