BA (or "Panic Brake Assist") is another feature to help reduce stopping distance for the driver who brakes quickly, but not hard enough to enter ABS. When it detects a rapid pressure increase (there is a master cylinder pressure sensor), it will basically turn on the pump and increase pressure rapidly to the point that the wheels go into lock, at which point ABS will take over to prevent wheel lock. If the driver releases the brake at any time, the system should also release brake pressure. It is possible that the threshold for activation is reduced momentarily in the event that the throttle is released quickly -- thus a quick move from on-throttle to on-brake, with a rapid brake pressure increase, will trigger a BA event.

This feature *should* still be working as long as the brake light switch is reliable and the brake pressure sensor is reliable. It probably does not depend on the yaw sensor.

I've noticed BA events when screwing around following one of my friends in his Z4 -- driving a little faster than I should've been -- I got out of a very hard throttle apply and spiked the pedal "lightly"... You'll hear the familiar 'grinding' noise and you might feel a hard pedal or a vibration in the pedal. I got a little more decel than I wanted but then again, that's sort of the intention of this feature.

When I re-read some of the old posts, it became clear to me that you guys are all tapping the brake while in an unstable situation (sounds like oversteer), intending to unload the rear and induce a little more slide. It is at this point, when you touch the brakes, that VDC intervenes and corrects the oversteer.

This feature is common in Mercedes-Benz vehicles and other OEMs, it just re-enables the VDC system to take care of the instability, recognizing that the car is not going where the wheel is pointed (yes, it was turned off by the driver) and the driver wants to stop -- for most drivers (probably > 95%) this is a handy "oh ****" feature and is intended to save your ***.

It sounds like most of you weekend racers have figured out that the yaw sensor will take down VDC -- but I think you'll find that for most situations on the street, it's better (and recommended) to keep everything on as it was developed.

In the last year I've sadly traded in my dream car (the '03 Z) for a '06 4d Frontier with VDC... A new baby means there are three of us now. The Frontier adds HDC (hill descent control -- not useful for the Z) and HSA (hill start assist, pretty sweet), along with all the other toys that the Z has.