Many of us are not trained by Mercedes, me included.
To be great at what you do, you must love it and be willing to invest in the tools and literature. You must be willing to spend the time to learn the causes of problems and be willing to listen to your customer.
Thanks for telling us the fix, but I am sure that some of us indpendents on the board could have found this as well. I'm sorry that your local independent let you down. I would think that they lack in one of the above departments.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS