how to program a mercedes-benz smart key?

In this blog, we will find out how to program a Mercedes Benz Smart Key. And answer the following questions: what are the features of the smart key? What to do if you lost the smart key?

How to program a Mercedes Benz smart key?

A Mercedes Benz Smart Key can be successfully programmed in the following steps

  • Identifying the Key and Key track
  • Additional key or replacement key
  • Registering vehicle in the workshop
  • Starting the programming 
  • Function check

Identifying the Key and Key track

Mercedes Benz is using a fourth generation of the drive authorization system in all of its latest models. There are 8 key tracks available for the programming of a smart key. Apart from 8 key tracks, there are also 3 segments on which a program key can be assigned.

 All the information about the current smart key and which track it is assigned to is available in the electronic ignition lock control unit. A technician can access this information from the Xentry diagnosis scanner. Once the key in use and the last or second last key in use is identified, the technician can proceed to program the new smart key.

As there are 8 individual key tracks and three segments for each key, a Mercedes Benz vehicle can have 24 functional keys in its lifetime. However, it should be noted that only one can remain functional on each track so a customer can request up to 8 working keys for a vehicle.

Additional key or replacement key

After the technician has identified the key number and key track, the next step is to determine whether to program an additional key or a replacement key. An additional key is like a spare key, it is programmed onto a different key track. If the customer recovers his original loss then there will be 3 working keys for the vehicle. 

The replacement key acts as a replacement for the loss of the inoperative original key. During programming, it is assigned to segment two of the original key track. Hence, even if the customer finds the lost key after programming the replacement key, the lost key will be rendered useless.

Replacement keys are usually programmed when the customer is sure that the smart key is stolen or permanently damaged. Additional keys are programmed only when customers request an additional key for the vehicle. Mercedes Benz has two smart keys as standard with the new vehicle.

The programming of the replacement key takes a long time compared to the programming of the additional key. This is due to the fact that the data from the previous segment is transferred to the new segment. The data consists of key codes that are used to verify the drive authorization in the electronic ignition lock control unit.

Registering vehicle in the workshop

The process of registering the vehicle in the workshop is very easy and fast. A technician connects the Xentry diagnosis scanner and initiates the process. The vehicle is connected to the centralised database for sending and receiving data. 

The key programming is only possible after the vehicle registration process is completed, therefore it is not possible to program a vehicle key at customers’ houses or outside of the authorised workshop. 

Starting the programming 

The programming process is initiated once the technician selects the appropriate key and key track for programming. The total time for programming is only a few minutes, once the programming is completed the Xentry system is removed from the vehicle and the key is inserted into the ignition lock for further teach-in process. The teach-in process can take time if it is a replacement key.  

Function check

A quick function check involves locking and unlocking the car and cycling through the ignition positions. Once the ignition is turned on and the message “ teach-in of the key” disappears from the cluster then the vehicle is started. 

During the complete smart key programming process, the vehicle is connected to the external battery charger. At least one work is required to successfully program additional or replacement keys. In case both the keys are lost then a full program key must be ordered from the factory. Authorised dealerships are equipped to take any parts order from a pre-programmed key after verifying the documents of the customers.

What are the features of the smart key?

The smart key is equipped with a transmitter and a receiver for the keyless go system, following are the features of the smart key:

  • Locking/unlocking

The vehicle can be locked or unlocked by a single press of the lock and unlock button on the smart key. A LED indicator flashes to indicate the button is pressed. locking / unlocking only works at a certain distance. Mercedes Benz also provides an MMC feature where the car can be locked or unlocked by a registered smartphone.

  • Global or selective locking/unlocking

Customers can choose to unlock only the driver door after pressing unlock only time, this feature is activated after pressing down both the lock and unlock buttons simultaneously for 7 seconds. The led will blink two times to indicate the feature is now active.

It is a good feature especially if the vehicle is used by a single customer and there is no need to unlock all the doors.

  • Keyless go

There are 4 additional antennas, 2  on either side of the vehicle and the other two in the luggage compartment and centre console of the vehicle. The keyless go antenna is always searching for the key. If any one of the antennae detects the key is within range and the driver is touching the door handle, it will unlock that particular door. 

There are two capacitive sensors located on the inside and the outside of all four door handles; the vehicle is locked after touching the sensor on the outside for one time. Similarly, if the customer touches the hand on the inside of the door handle the vehicle is unlocked.

The sensor is located in different locations but care should be taken not to touch both the sensors simultaneously as this might confuse the keyless go system.

What to do if you lost the smart key?

If you lost the smart key then immediately report it to the authorised dealership. The dealership will recommend blocking the key track. Blocking the key track of the lost key means even if someone finds the key, they cannot gain access to the vehicle. If the customer is sure that the key is permanently lost then the dealership will program a replacement key for the customer. A lost or stolen key is not covered under any warranty and it is the sole responsibility of the customer to keep the key secured. 

Other articles about Mercedes Benz you may be interested in

What are the best used Mercedes Benz models to buy?

What is a Mercedes Benz key made up of?

Mercedes Benz e350 luxury vs E350 sports model?


Mercedes Benz smart keys are advanced and there are many features built-in which make using the smart key very convenient. Customers can even open or close all the windows by simply long-pressing the lock / unlock button. If the low battery indicator on the key is on then the battery of the key must be replaced.