Message “Theft protection Active Mercedes”

Component protection (theft protection active)

Since 2010, Mercedes Comand, Audio 20, Becker modules are equipped with an anti-theft protection. This protection works as follows.

When installing the radio (at the factory), an identification key is stored in the unit. This key belongs to 1 specific car, namely the car in which the device is installed. This key is provided with a pin code so that, if necessary, this key can be re-paired. This pin code is digitally stored in the vehicle file of the car

At every start or after so many starts, it is checked whether the key in the device still matches the key in the car. If this is not the case (anymore), the user will receive the message “Theft protection Active” and the key must be re-learned using this pin code.


There are some known problems with this component protection that cause it to go off "spontaneously" while driving.

  • After replacing the ignition switch at (ML/GL/R class 2009-2010)
  • After replacing the engine control unit
  • Problem in the device itself
  • CAN Interruptions
  • Device was installed later or recently replaced and not taught in correctly


In most cases, re-learning the device is sufficient to solve the problem. The learning is done with the official software of the manufacturer and several steps are followed. It is important that the device is registered on the vehicle card with the relevant car so that the identification key can be re-paired.

If re-learning does not succeed, there is often a problem in the device where the key is not or not correctly stored in the system