Mercedes Pre-safe Functions Limited [Meaning and How to Reset]

Driving can be less exciting when you see a warning message and you have no idea what it means. The vehicle communicates to the driver in several ways and one of the messages it might send is “Pre-safe function limited”.

The pre-safe function is an advanced safety feature in modern vehicles like Mercedes that helps prevent accidents and reduce the severity of injuries in the event of a collision. This system uses various sensors and technologies to detect potential hazards and activate protective measures before a crash occurs.

However, despite its advanced capabilities, the PRE-SAFE function has certain limitations and situations where it may not be fully effective.

In this post, we will examine some typical reasons your Mercedes Benz is displaying the warning message PRE-SAFE Function Limited.

What is Mercedes Pre-safe Function?

Mercedes Pre-Safe is a safety system with a network of sensors that assists in detecting collisions and other abnormalities while driving. It is a preventive measure that guarantees the driver and passengers remain secure behind the wheel throughout and after an accident to lessen harm to the driver and passengers. 

Also, this safety feature gets the car ready for an oncoming impact by adjusting the head restraints and tightening the front seatbelts. 

How Does the Pre-safe Mercedes-Benz System Work?

When your Mercedes-Benz vehicle detects that an accident is about to occur, the system will initiate the following steps to help protect you:

  • Tightens safety belts to protect passengers from injury.
  • Front head restraints adjust themselves for maximum crash protection.
  • If a rollover is possible, the windows and sunroof will close. This will help to prevent debris from entering the cabin.

This system is a highly sophisticated technological system that depends on several parts. As a result, in a system of this complexity, there is a higher likelihood of something going wrong. It could be something as simple as dusty sensors or as complex as malfunctioning software.

What Does “Pre-safe Functions Limited” Mean?

The pre-safe functions limited is a warning message that indicates there is an issue with your pre-safe system, which would require car servicing. This typically appears when a sensor needs to be adjusted or cleaned, and it may also appear if and when your sensors become obstructed by snow, ice, or mud.

Causes of Mercedes Pre-safe Functions Limited

1. Malfunctioning Software

Bugs can cause well-coded software to malfunction even though professionals have coded it. As a result, if the software that the PRE-SAFE system uses does not respond appropriately to the input data it receives from the radar sensors, you will see this warning. 

Software errors or bugs frequently caused pre-SAFE Function Limited warnings. However, you can easily fix it by installing the most recent Mercedes software update on the system. You can do this yourself or consult a Mercedes professional mechanic to assist you. 

2. Loose Throttle Body Switch Plug

Your dashboard may display “pre-safe function limited” as a result of a loose throttle body switch connection. If this is the case, your Mercedes will disable the PRE-SAFE system and flash this warning message.

Since these safety systems also get their information from the throttle body, other warning lights typically accompany the alert, such as the ABS or Traction Control. The connections should be examined to make sure they are secure and clear of corrosion.

3. Dirty Sensors

The pre-safe system uses a system of radar sensors mounted on the front of your car. When driving under challenging road conditions, these sensors may become dirty or blocked by debris. This could be the reason the PRE-SAFE Function Limited warning message is on your dashboard. 

Cleaning the sensors can help them become free of snow or dirt, which will make the warning message go away.

4. Water Droplets or Snow Particles

The sensitive sensors in the pre-safe systems are vulnerable to harm from moisture or water. They can not perform effectively if these sensors are covered in snow or water. The display of the warning notice could indicate the presence of snow or water particles.

5. Faulty Sensor Cables

To monitor the environment around your vehicle, a PRE-SAFE system relies on sensors. The sensors must always remain linked to the car to receive the required data. However, a system open circuit can occur by connecting cables that have corroded and broken over time.

You have to identify loose connections and tighten or replace them if the cables are damaged to fix this issue. 

6. Low Battery Voltage

If the vehicle’s battery voltage is low, the PRE-SAFE system may constrain its operation. To ensure that the PRE-SAFE system performs as expected, it is crucial to keep adequate battery voltage in the car. This is so that the system can operate as intended, which needs a certain amount of power.

How to Fix Mercedes “Pre-Safe Functions Limited” Warning Message

If your radar sensors are clean but the Pre-safe functions limited message is still appearing, then there most likely is a problem with one of the radar sensors.

Examine the front-mounted radars; the number and type of radars you have to rely on the specifications of the car. To resolve this warning message, you must replace the radar sensor.

Check for evidence of water or moisture, wiring damage, smelly connector plugs, or any other indications of such damage and fix it.

Read: Green Car Light on Dashboard


Whenever you see the alert pre-safe Function Limited, it simply means that something is wrong with the pre-safe system.

It could be a malfunctioning sensor or a software issue with the system. Debris might contaminate them, obstruct them, or moisture might harm them.

Therefore, it’s essential to have your pre-safe system checked by a skilled technician as soon as possible if you see this message. The system may require repair or replacement, depending on the cause of the issue.