How to Reset a Mercedes M Class Radio

by Cassandra Tribe
isolated luxury crossover suv car high speed image by alma_sacra from

It may be necessary to reset a Mercedes M Class radio should the radio or battery be disconnected or the battery become completely drained. When the radio receives power again, it will be in a locked and unusable state. The LCD display will read "Enter Code." The security code assigned to the vehicle must be entered to reset the radio and unlock it.

Step 1

Disconnect the negative cable from the battery with a socket wrench and then disconnect the positive cable as well. Wait 30 minutes to allow for the vehicle's emergency power store to discharge completely before proceeding with the project.

Step 2

Reconnect the positive cable to the positive terminal on the battery with a socket wrench and then reconnect the negative cable to the battery.

Step 3

Punch in the five number vehicle security code on the radio keypad. The security code is included with the owner's manual.

Call a local Mercedes-Benz dealership and give them the VIN of the vehicle and the radio's serial number to receive the code if the manual cannot be located. The radio's serial number can be found on the identification plate located on the underside of the radio. Pull the knobs off the radio, remove the face plate by prying it off by hand and the radio may be pulled out far enough to read the plate.


  • If the wrong code is entered, wait an hour for the error message to clear before trying again.


  • Do not attempt to remove the radio and install it in another vehicle. While the security code will unlock it for use in the new vehicle, the security system in the original one will disable the car and it cannot be unlocked without the radio installed.

Items you will need

  • Socket set
  • Security code
  • Radio serial number (if needed)
  • VIN number (if needed)
  • Mercedes dealership contact number (if needed)

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