Mercedes Benz employs a system called sensotronic brake control (SBC) for the W211 E, W230 SL,and W219 CLS class variants.
This is a brake by wire system that no longer relies on the driver to produce the hydraulic pressure required to operate the
Sensors on the brake pedal inform the computer how the pedal is pressed, eg how far, how fast etc. The computer will then
dissipate the required force to each wheel.
The control units have a factory set service life after which an error
OPERATING TIME OF COMPONENT A7/3 IS EXCEEDED
(SBC HYDRAULIC UNIT).
C2358 service threshold reached
STOP Brakes Defective
Please see Pics
In many cases this simply means that the number of preset brake pedal presses has been exceeded and the unit needs replacing
at a cost of £1000+, regardless of its operating condition, However it is now possible to reset the existing unit for
considerably less than the price of replacement.