If you can only read DME/EGS from dash, you lost the pin that drives the other modules. I had a dirty connection on wife's and couldn't reset or read codes at all then a little contact cleaner and works again.

I think noise on the comm line is a big cause of these issues; I've heard of abs module putting noise on lines causing this sort of issue

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)