Why don’t Mercedes Benz cars have a remote start?

This blog will answer the following questions: why don’t Mercedes Benz cars have a remote start? How does a remote start work? How to retrofit a remote start in a Mercedes Benz car? 

Why don’t Mercedes Benz cars have a remote start?

Mercedes Benz cars don’t have a remote start because of the following reasons:

• Lack of hardware
• Security risks
• Preserve key batteries
• Manual transmissions

All the above-mentioned reasons are explained in detail below:

Lack of hardware.

A remote start function requires additional components like electrical wiring harnesses, control units and long-range secure antennas. The control units also need programming to be able to function and communicate with the other control units in the car.

Mercedes Benz cars also have theft-relevant parts like electronic ignition switch, steering lock, engine and transmission control unit. The drive authorization code is related to all the control units in the form of a start enable signal.

Once a start enable signal is issued by all the control units, the starter motor then cranks the engine. Without the circuit 50 or start enable signal the engine cannot be started in any Mercedes Benz cars.

Therefore, Mercedes Benz cars do not have remote start as the components needed to remotely start a Mercedes Benz car are not present in the vehicle.

Security risks

When the vehicle is started remotely, the fuel pumps are active until the driver turns off the ignition. If unauthorised access is gained into the vehicle when it is remotely started, it is possible to drive it even if the key is not present in the vehicle.

Mercedes Benz cars have a drive authorization system that uses rolling codes and hash codes to verify the key. After the codes are verified in the electronic ignition lock, the ignition cycle or drive cycle is started and the vehicle does not need new codes to continue running.

New codes are only needed once the previous ignition cycle is ended by either turning the key in the ‘0’ position or pressing on the start-stop switch.

There is a security risk in remotely starting the vehicle, most remote start systems available in the market allow drivers to set a timer for the engine. However, as the key has already provided the authorization codes, it is possible to steal the car while the engine is running.

Small Key batteries

Mercedes Benz uses smart key fobs for locking and unlocking cars. There are special features like global and selective unlock, and convenient opening and closing of all the windows and sunroof.

The key battery is already under a heavy load, there is a battery-saving function built into the microcontroller inside the key. However, for a remote start, the driver needs to press the buttons on the keys multiple times. 

The transmitter inside the key has to send the signal multiple times which consumes the key battery quickly. The latest key fob is also powered by a single battery so adding a remote start function will reduce the battery life of the key fob.

Manual transmissions

Mercedes Benz offers a choice of manual transmission in some models like the A-Class, B class, CLA etc. A steering lock is present as an additional security measure because there is no parking gear in the manual transmission.

In order to start the car the clutch needs to be depressed in the vehicle and the manual transmission must also be in neutral. The presence of a driver is needed in modes with manual transmission. hence, it is not possible to integrate a remote start function without making hardware changes.

How does a remote start work?

A remote start system works by transferring the drive authorization codes directly to the electronic ignition control unit remotely. It uses a dedicated antenna to receive the key codes and transfer them to the EZS. After the EZS confirms the key codes it will send the start to enable signal to the engine control unit.

The start-enabled signal is also confirmed by other theft-relevant parts like the steering lock, transmission control unit and ESP control unit. Another method is to send the start enable signal via a smartphone. Customers’ smartphones are registered as a key in the EZS.

The smartphone will transfer the necessary key codes required to start the vehicle. In 2016 Mercedes Benz also introduced the mbrace or Mercedes Me connect. A HERMES module integrated with the electronic E sim is used for drive authorization instead of a digital key fob.

This method allows the customer to remotely start the engine and also set the duration for which the engine will keep running. Mercedes Benz designed a smartphone app for IOS and Android operating systems. 

Customers’ are required to download the app to use features like remote engine start, locking or unlocking the vehicle and also setting up a geofence. Customers will get a notification if the vehicle breaches the boundary.

How to retrofit a remote start in a Mercedes Benz car?

There are many aftermarket products available for Mercedes Benz cars that can add remote start capabilities without modifying too many things. Some of the popular ones are mentioned in the table below

The aftermarket remote start kit contains a control unit with a dedicated antenna module, wiring harnesses and a tool to remove the electronic ignition lock switch. The installation procedure is as follows:

• Remove the driver side lower panel of the dashboard, unscrew the electronic ignition switch and place it downwards.
• Install the wiring harness in the remote start system kit and plug all the connectors in the EZS
• Install the remote start system control unit, in the passenger footwell, and connect the CAN high and CNA low line to the interior CAN distributor. The interior CAN distributor is identified by brown and brown red CAN lines.
• Connect the power supply and ground signal to the remote start control unit
• Install all the removed panels and the electronic ignition switch in reverse order.

Perform a function check, the engine will start after pressing the panic button on the key fob for half a second and then release. Indicators will also flash once to confirm the key press and the engine starts within 5 seconds.

By default, the engine can run for 15 min, make sure to not unlock the vehicle and keep the engine running as it is possible to drive the vehicle. The remote start system is deactivated when the key is inserted into the electronic ignition lock.

Other articles about Mercedes Benz you may be interested in

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Conclusion

This blog listed the reasons behind the absence of the remote start function in Mercedes Benz cars. There are aftermarket remote start systems available that can remotely start old Mercedes Benz cars. The latest Mercedes Benz models come with an inbuilt  e-sim  and the remote start function is available from the mobile phone app.