See also:

Problems with PARKTRONIC
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Important safety notes
WARNING When leaving the vehicle, always remove the SmartKey from the ignition lock. Always take the SmartKey with you and lock the vehicle. Do not leave children unattended in the vehicle, ...

Applying automatically
Your vehicle's electric parking brake is automatically applied if DISTRONIC PLUS or the HOLD function bring the vehicle to a standstill, or are engaged to keep the vehicle stationary. In addit ...