Can a Mercedes Benz Key fob be reprogrammed?

This article will provide knowledge regarding the drive authorization system used in Mercedes Benz passenger cars, also programming of key fobs and answer the questions like  “can you reprogramme a Mercedes key fob?”

Can a Mercedes key be reprogrammed?

To put it in a simple way, if you have a key which already belongs to a vehicle then it cannot be reprogrammed and be used on another vehicle. As the key fobs are coded to the vehicle and programming can only take place once.

Each vehicle comes with two sets of key fobs. Programming of key fobs can be required in the  following situations.

  •  when the key fob is stolen or lost.
  • When the existing key fob is damaged
  • When an additional key fob is requested by the customer.

How does the Mercedes Benz drive authorization system work?

In a Mercedes benz vehicle a drive authorization system consists of four to five theft relevant components. Each time a driver inserts key fob into the vehicle a drive authorization code is verified in all theft relevant components, the vehicle will only start when the code is verified by these components and a start enable signal is received by the vehicle onboard computer.  

What are the theft relevant components?

The theft relevant components consist of an electronic ignition switch, engine control unit, the transmission control unit, steering lock(only valid for manual gearbox) and electronic stability program control unit. 

These control units are like individual computers all connected via CAN controller area network protocol. The drive authorization takes place in an electronic lock control unit, which is mostly located on the side of the steering wheel, where key can be inserted. 

The key fob can transmit two types of codes namely rolling code and hash code. Rolling code mainly is used for access authorization which means gaining entry into the vehicle while hash code is more complex which allows for access to start and drive the vehicle.

What do you mean by Additional Key and spare or replacement key?

Programming of key incorporates assigning a key to a specific key track which is present in the electronic ignition key. This is done by a diagnostics tool or at a key station available at the authorized service center. Each vehicle has eight key tracks and consists of three segments but only one key fob can be used at any given time on an individual key track. 

This means a vehicle can have a total of twenty four keys during an entire service life of the vehicle. In the event of a lost or stolen key, there is a way to identify the key track and block it so misuse of the key fob can be prevented. This key track can be activated again if a customer finds the key.

Replacement Key

In the event when a customer cannot find the lost/ stolen key then it is possible to programme a new key fob to the same key track but new segment 2. This will make the old key fob inoperative and new key will act as a replacement key

Additional Key

When a customer requests more than two keys for the vehicle, it is possible to programme a key fob to a different key track. This way the existing two keys will remain operational and customer will gain an additional key for the vehicle. A Vehicle can have six additional keys in addition to the two original keys which comes as standard.

The time required to programme replacement key is more when compared to programming additional key.

Understanding difference between initializing and programming key fobs

Many types of procedures are available online in written articles and videos. These procedures mostly involve a sequence of locking and unlocking the vehicle after pressing lock and unlock buttons simultaneously. Make no mistake such procedures are a waste of time and do not reprogramme key fob. Initialization is basically  electronic ignition switch recognizing a new key fob when it is first inserted. It is a one time process and if there are already working key fobs then it is  not required to be re-initialized.

Mercedes Benz DAS generations

Since the use of electronic key fobs became mainstream, Mercedes Benz has had a total of four DAS generations which can be distinguished based on the type of key fobs. 

Das 3 key

das 4 key

The latest drive authorization system (DAS) is generation 4 which allows for remote programming of key fobs at authorized dealerships which will greatly reduce repair times as dealerships can keep blank, unprogrammed keys in their stock. DAS 4 also allows use of Smartphones to lock and unlock newer models.

Other articles about Mercedes Benz you may be interested in

Can a Mercedes Benz overturn?

Can a Mercedes Benz be stolen?

Which is the best Mercedes Benz AMG car?


This article provided an insight into the drive authorization system used in a Mercedes Benz vehicle and also explained why its not possible to reprogramme a Mercedes Key fob. Special equipment like diagnostic tool with proprietary software is required to read and programme key fobs which are only available at the authorized service centers.

FAQs:Can a mercedes key fob be reprogrammed

How do I reprogramme my Mercedes Benz Key?

Your existing Mercedes Benz Key is already Programmed and operational. Incase Key fob is inoperative kindly check key fob batteries and Try to unlock vehicle with spare key. If both Keys are inoperative please contact the nearest Mercedes Benz workshop.

Can the existing Key fob be reprogrammed?

No, It is not possible to reprogramme any existing key fobs. You will have to visit Mercedes Benz authorized dealership and purchase a New key fob for the vehicle. Mechanical key inside the key fob can be reused.

How do car dealership program key fobs?

Car dealerships have authorized personnel trained in programming drive authorization related components. A diagnostic tool with special access to the central vehicle database is connected to the vehicle and after the technician identifies the correct key track, a new spare key is assigned to the vehicle permanently.

How long does it take to programme a Mercedes Benz Key?

It can take two to three hours to programme a replacement key, however additional keys can be programmed within one hour. In certain special circumstances it can take more than 4 hours to successfully programme and initialize a new key to the vehicle.

Can you programme a key fob without the original?

Yes, even if original keys are not present, a new key fob can be programmed to the vehicle as all the drive authorization related data is present in the electronic ignition lock.

Why is my key fob not being detected?

In the event of the key fob not being detected, make sure to check the battery in the key fob and try an alternate key for the vehicle. If the main battery of the vehicle is drained it won’t be possible to detect the key fob. Also it can be a problem with the electronic ignition lock or the key fob itself which can lead to the vehicle not starting.