Vehicle is 2014 ML 350 Bluetec
recently the light came on.. zero issue.. then at idle about a week later now it’s having a bit of a rough idle, but only in park.. in gear it’s fine.
doesnt madly fluctuate rpm.. just rougher then usual.
110,000kms
due for B service in 10,000

Also has stored clyinder 1 and stored cylinder 4
thats front of engine.
not sure why 1 is permeant and 4 is only stored.
I can check some simple stuff tomorrow, any suggestions? Ive hard the diesel isn’t great this winter, but just water in it.. The filter / separator should be able to keep up and there should be a code if it sensed that.