I think you have it backwards - both DSC and DTC are on by default, pushing the DTC button once turns off DTC but leaves DSC on, and holding it turns both off. (May have just been a typo on your part)
Originally Posted by jcl10
That isn't what DTC is for. The confusion starts with the BMW labelling system for warning lights and the button.
In normal state, no lights, you have DSC (Dynamic Stability Control) and DTC (Dynamic Traction Control), by default. DSC helps with sliding, DTC puts a brake on to stop a wheel from spinning. There is a low system threshold for a spinning wheel, meaning the system (nanny) intervenes quite early.
Pushing the button once turns off DSC, but keeps DTC on. It allows more wheelspin than the standard setting (fewer nannies). This is designed to be used if you try to get going at slow speeds and the road is so slippery that you have no throttle response, ie the computer is limiting throttle because of wheel spin. Allowing some wheel spin can get you up a hill or get you moving sometimes when the system would otherwise stop you. Once you are moving, it is worth putting turning DTC off (back to normal state) for most drivers.
Holding the button for longer turns everything off. Good for track days, or playing around in parking lots to find out the limits of your car.
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