See also:

Deactivating HDC
Press the button again; the LED goes out. HDC is automatically deactivated above approx. 37 mph/60 km/h. ...

Following part replacement
The same breaking in procedures should be observed if any of the components mentioned above have to be renewed in the course of the vehicle's operating life. ...

Activating HDC
Activating HDC Press the button; the LED above the button lights up. The LED flashes when the brakes are applied automatically. ...