This is the problem with R170s, a lot of scanners don't talk to the modules even tho they are detected and one fault can throw up a mess of faulty components .. you can easily end up playing 'parts darts'
iCarsoft MB II (£140) is adequate in most instances but won't talk to the roof or the aircon, will vaguely point you in the right direction with other modules
Autel md802/805/808 (£200ish) seems to fair a whole lot better all around - there are members on here that quite like their Autels
Merc SDS (£400) is on a whole different level and will tell you everything apparently - resident gurus will confirm that
It may be worth your while to get it scanned by Mercedes before you disappear down a rabbit hole
If it costs less than a £400 ish SDS then it is no use with faults such as this and many others.
SDS will do absolutely everything you will ever need, and some.
I am a professional diagnostic / repair workshop, with many different marques Dealer level kit, including 2 SDS machines. I also have 3 good Generic Machines costing 4 to 6 times £400, and even those machines only access a maximum of 80% of all areas / codes on Mercedes, and they don't have the Guided Testing Diagnostic, Developer Mode, (even an MB Dealer doesn't have Developer allowed on their machines), Component Locator, Workshop Manuals, Parts Catalogue etc etc etc.
The first time you think of chucking parts at the problem, bite that bullet, buy SDS and it will pay for itself, and then many times over across the years.
HTH, Cheers Dave