Can you unlock a Mercedes door without a key?

In this blog, we find out under what circumstances it is possible to unlock a Mercedes door without a key? And also answer the following questions: Can a Mercedes Benz lock itself with the key still inside? What to do if you lose your Mercedes car key? Is it possible to drive a Mercedes without a key?

Can you unlock a Mercedes door without a key?

No, it is not possible to unlock a Mercedes door without a key; however, the door can be unlocked in the following circumstances.

  •  If the key fob is lost but the Mechanical key is present

Mercedes Benz uses a combination of infrared and radio signals to transmit key codes to the vehicles. The codes are transmitted when the customer actuates the lock or unlock button. There is a mechanical key stored inside the key fob; it can be removed and used to gain access to the vehicle. A mechanical door lock is present on the driver’s side. The key barrel is covered by a protective panel; the mechanical key can be used to remove the protective cover and insert the key into the door lock.

It is important to note that this method only allows for access to the vehicle. Mercedes Benz discontinued the use of cylindrical ignition switches and all the models use electronic ignition locks. Therefore, even if the customer gains access to the vehicle it is not possible to start the engine and drive the vehicle with only a mechanical key present.

  • If Smartphone is authorised

Mercedes Benz introduced smartphone keys in selected markets, this is different from the Mercedes mbrace of the Mercedes ME app. The driver authorization codes are stored in the smartphone and after verifying the customer password or fingerprint, the vehicle can be unlocked and even started remotely. In the electronic ignition lock control unit, there are 8 key tracks available that can be used to program additional keys. 

Mercedes Benz provides 2 keyfobs with the vehicle and if customers want, the smartphone sim can also be programmed to act as an additional key on one of the empty key tracks. Currently this feature is only present in the limited markets as it requires a compatible sim card in the smartphone so that it can act as an additional key and also keep the drive authorization codes secured at the same time.

  • If the Mercedes Me connect app is working

 The new telematics generation (NTG) 6.0 Mercedes Benz command operating system comes integrated with the Mercedes Benz user experience interface. A HERMES control unit with integrated e-sim is installed in the overhead control panel. After the purchase of the vehicle is completed, customers can download the Mercedes Me app from IOS and Android stores. 

Through this app, it is possible to remotely lock or unlock the vehicle as long as the vehicle and the smartphone are in the cellular network range. The e-sim in the vehicle provided internet access for the Mercedes me features. There is no requirement for a special sim card in the smartphone as the sim itself has nothing to do with the drive authorization of the vehicle. The electronic sim in the vehicle receives information from the customer from the Mercedes ME app and drive authorization is granted. 

Through Mercedes Me connect, it is possible to start the engine and activate features like pre-entry climate control.

 Can a Mercedes Benz lock itself with the key still inside?

Yes, a Mercedes Benz can lock the doors with the key still inside because there is a battery disconnect switch in the latest models. The battery disconnect switch is programmed to open and isolate all the control units from the battery so that the main battery does not get completely discharged. The battery disconnect switch is opened by the front signal actuation and acquisition module. Before the switch is opened, all the windows are closed, the parking brake is engaged and doors are locked even if the key is still inside.

Therefore it is not advised to leave the key inside as vehicle battery monitoring systems are constantly checking the battery voltage and in order to preserve the ability for the next engine start; the vehicle will go into battery saving mode.

The Mercedes Benz models with the keyless go systems have a fool-proof system in place but only if the key is kept in the luggage compartment. A dedicated keyless go antenna can detect the position of the key in the trunk. If a customer forgets the key is in the luggage compartment then the trunk lock is actuated automatically and the boot lid is opened. Unfortunately, the system does not work if the key is in the passenger compartment and the customer closes the door.

What to do if you lose your Mercedes Benz car Key?

In the event, the Mercedes Benz car key is lost then the following are the important steps to do on priority.

  • Locate and use the spare key, Mercedes Benz provides 2 keys with each vehicle
  • Visit the nearest dealership and block the lost key so that even if it is found, unauthorised access can be prevented.
  • The blocked key can be enabled again so if there is a possibility of recovering the lost key, then the dealership.
  • If the key is permanently lost or beyond recovery then a replacement key can be ordered from the dealership.

When ordering a replacement key or a spare key, the dealership will need the original registration document of the vehicle and verify the customer’s identity as the key is a theft-relevant part. When the replacement key programming procedure is completed, the lost key becomes permanently inactive.

Is it possible to drive a Mercedes Benz car without the key?

No, it is not possible to drive a Mercedes Benz car without the key. Mercedes Benz is currently using the fourth generation of the drive authorization system. There are two types of codes used for the access authorization and driver authorization of the vehicle. 

The access authorization codes are transmitted by the key to the FM amplifier in the vehicle, from there the electronic ignition lock control unit verifies them and grants access to the vehicle. Drive authorization codes on the other hand are verified by a more secure means, a special antenna in the central console directly receives drive authorization codes and sends the codes to the electronic ignition lock. Therefore, the key must be inside the vehicle in order to drive it.

Other articles about Mercedes Benz you may be interested in

What is the maintenance cost of the Mercedes Benz S550?

Which is the most reliable Mercedes Benz Car that was launched in 2020?

Why do Mercedes Benz cars have two batteries?


Mercedes Benz uses the most secure driver authorization system in the automotive industry. Customers can remotely access vehicles through the smartphone app and with optional extra packages like a remote Parking pilot, it is possible to drive the vehicle for a few metres so that it’s out of tight parking space. It is the customers’ responsibility to keep the key secured as without it there are no legal means to gain entry into the vehicle.