See also:

The concept
The parking brake is primarily intended to prevent the vehicle from rolling while parked; it brakes the rear wheels. ...

Coolant temperature
Should the coolant, and with it the engine, become too hot, a Check Control message is displayed. Check the coolant level. ...

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