There are 2 sets of contacts on the brake switch which work opposite to each other, i.e. when 1 is open the other is closed and visa versa. When I had fuse F35 blow, due to a reversing light problem, I got ABS/VDC failure. This is because fuse F35 feeds the brake pedal NOT pressed switch contact which normally sends a +ve signal from the brake switch to the ABS control unit with the pedal NOT pressed (to inhibit ABS when there is no braking). The ABS control unit also gets a signal from the other switch contact on the brake switch which tells it the brake pedal is pressed. This is why I was getting ABS/VDC failure, the ABS control unit knew the pedal wasn't pressed, from one contact, but wasn't getting a signal to say the brake pedal was not pressed (due to blown fuse) from the other contact so it threw a wobbler and a failure. I got a Brake Pedal Switch failure in FiatECUScaner for this fault. I'm guessing that if the switch fails in some other way you won't get a fault code ... in which case why does the ABS control unit throw a fault ? Sounds like a bug to me. As I said elsewhere, if I started the car with the brake pedal depressed I got no failure. I only got the failure the instant I released the brake pedal and the ABS control unit realised that one of the switch contacts wasn't working.
The brake switch probably causes problems because any slight mismatch between 1 contact opening and the other closing will throw an ABS error. All in all, not the most intelligent bit of design since you loose ABS all for the sake of a blown fuse that protects only non safety critical functions (reversing light, cruise control, climate control light !). Luckily it doesn't affect the EBD.