See also:

Mercedes-Benz M-Class Owners Manual
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NECK-PRO head restraints
Resetting the NECK-PRO head restraints requires a lot of strength. If you have difficulty resetting the NECK-PRO head restraints, have this work carried out at a qualified specialist workshop, e.g ...

Immobilizer
The immobilizer prevents your vehicle from being started without the correct SmartKey. When leaving the vehicle, always take the SmartKey with you and lock the vehicle. The engine can be started ...