A Few W211 SBC Code/Message Questions
 

So we know that when we get the white "Visit Workshop" message and we discover it's related to the the SBC, it's due to one of the following:

C249F Operating time of a7/3 (hydraulic unit) is exceeded
C2131 Pressure Reservoir faulty
C235C or C235A Service threshold reached

If it's the C249F or C235, it sounds like it's around 600k actuations for the later (or updated) SBC units....although there's no exact number because other factors are apparently taken into account.

Am I correct that, if one lets things go and sees the dreaded red message of death, it's not because some new count threshold has been reach but rather because there has been actual mechanical failure? In other words, it can't possibly be that the red message would appear if the unit were still mechanically functional, right?

Also, anyone want to hazard a guess as to how much margin of safety MB engineers built in between the white message and the red message? If one were away on long trip, would it be reasonable to conclude that it's safe to drive home several hundred miles without worrying about failure?

I thought I had problems when a bulb blew out on my 96E300D. Reading the posts on members with newer vehicles, it seems that Mercedes has built in a "self destruct" program with all its new electronics. As you mention, I would hate to have a long drive ahead of me and have one of those error messages pop up out of the blue. I would be sitting on pins and needles wondering if the car was going to go into "limp mode" at any moment. Not my cup of tea!!!!!

Think of it as an early warning system...which I'm simply trying better to understand.

The SBC is a great braking system....if once every 200k miles or so it needs to be serviced that's not a big deal.