Active Curve System Malfunction (Causes, Diagnosis + Solutions)

active curve system malfunction

The Active Curve System (ACS) is a sophisticated suspension technology integrated into Mercedes-Benz vehicles, designed to provide optimal stability and comfort.

This advanced system automatically adjusts the suspension according to the vehicle’s speed, terrain, and driving conditions. However, there have been reported cases of the Active Curve System malfunctioning, causing concerns among owners and potential buyers.

Here are a few steps you need to take to fix the active curve system malfunction, which includes:

  1. Component Replacement
  2. Software Updates
  3. Hydraulic System Repair
  4. Electrical Repairs

In this comprehensive guide, we will discuss the causes, diagnosis, and solutions for the active curve system malfunction.

Understanding the Active Curve System

Before delving into the malfunction issues, it’s essential to understand how the Active Curve System works and its purpose in a vehicle.


The Active Curve System works in conjunction with the Adaptive Damping System (ADS) and AIRMATIC air suspension to provide a seamless driving experience.

It uses a combination of sensors, actuators, and control units to adjust the vehicle’s suspension according to various driving conditions. This results in improved traction, stability, and comfort for the driver and passengers.

Key Components

The primary components of the Active Curve System include:

  1. Sensors: These devices measure various parameters such as vehicle speed, steering angle, and lateral acceleration to determine the required suspension adjustments.
  2. Actuators: These are responsible for making the necessary changes to the suspension settings based on the input received from the sensors.
  3. Control Units: The control units process the sensor data and send commands to the actuators to adjust the suspension settings accordingly.

How does the Active Curve System work?

The Active Curve System is a suspension system that uses hydraulics to adjust the stabilizer bars in real-time to reduce body roll during cornering, ensuring a smoother ride.

The system is only available on certain Mercedes-Benz models, such as the GL Class (X166), and can be expensive to replace.

Common Causes of Active Curve System Malfunction

There are several factors that can lead to the malfunction of the Active Curve System. Some of the common causes include:

1. Component Failure

One of the primary reasons for the Active Curve System malfunction is the failure of its components. This can include sensor malfunctions, damaged actuators, or faulty control units.

2. Software Issues

The Active Curve System relies on complex algorithms to process the sensor data and make appropriate adjustments to the suspension settings.

Software glitches or outdated firmware can cause the system to malfunction, leading to poor performance or even complete failure.

3. Hydraulic Fluid Leaks

The Active Curve System uses hydraulic fluid to control the suspension settings. A leak in the hydraulic system can result in the malfunction of the active curve system, as it compromises the system’s ability to maintain the appropriate fluid pressure.

4. Electrical Problems

Electrical issues, such as damaged wiring or corroded connectors, can compromise the communication between the system’s components, leading to a malfunction.

Identifying the Signs of Active Curve System Malfunction

To diagnose the malfunction, it’s essential to recognize the warning signs that indicate a problem with the Active Curve System. Some common symptoms include:

Warning Messages

One of the most apparent signs of an Active Curve System malfunction is the appearance of warning messages on the vehicle’s instrument cluster.

These messages can include “Active Curve System Inoperative” or “Service Active Curve System.” These messages indicate that the system has detected a fault and requires immediate attention.

Poor Handling

A malfunctioning Active Curve System can result in suboptimal suspension settings, leading to poor handling and reduced stability.

Drivers may notice a decrease in cornering ability or an increase in body roll during turns.

Uneven Tire Wear

If the Active Curve System fails to adjust the suspension settings correctly, it can lead to uneven tire wear. This is because the suspension’s improper alignment can cause excessive stress on specific tire areas, leading to premature wear.

Reduced Ride Comfort

The Active Curve System plays a significant role in maintaining a comfortable ride by adjusting the suspension settings to suit various driving conditions.

A malfunction can result in a harsher ride, as the system fails to make the necessary adjustments.

Diagnosing the Active Curve System Malfunction

Once the signs of a malfunction have been identified, the next step is diagnosing the root cause of the problem. This process typically involves:

Consultation with a Professional

Given the complexity of the Active Curve System, it’s essential to consult a qualified technician to diagnose the malfunction.

They will have the necessary knowledge, experience, and tools to pinpoint the issue and recommend the appropriate course of action.

Diagnostic Scans

A professional technician will likely perform a diagnostic scan to identify any fault codes related to the Active Curve System malfunction.

This will help them determine if the problem lies within the system’s components, software, or wiring.

Visual Inspection

In addition to diagnostic scans, a technician may also conduct a visual inspection of the Active Curve System components.

This can include checking for hydraulic fluid leaks, damaged wiring, or corroded connectors that may be contributing to the malfunction.

Solutions for Active Curve System Malfunction

After diagnosing the root cause of the malfunction, the technician will recommend the appropriate solution. Some possible solutions include:

Component Replacement

If the malfunction is due to a failed component, such as a sensor, actuator, or control unit, the technician will recommend replacing the faulty part.

Software Updates

In cases where the malfunction is caused by software issues, the technician may suggest updating the system’s firmware to resolve the problem.

Hydraulic System Repair

If a hydraulic fluid leak is causing the malfunction, the technician will repair the leak and refill the system with the appropriate fluid.

Electrical Repairs

For malfunctions related to electrical problems, the technician will repair or replace any damaged wiring or connectors to restore proper communication between the system’s components.

Preventative Maintenance for Active Curve System

To avoid potential malfunctions, it’s essential to perform regular maintenance on the Active Curve System. This can include:

Regular Inspections

Having the system inspected by a professional technician at regular intervals can help identify potential issues before they escalate into more significant problems.

Fluid Checks

Ensuring the hydraulic fluid levels are maintained and the fluid is in good condition can help prevent malfunctions related to hydraulic system leaks.

Software Updates

Keeping the Active Curve System’s software up-to-date can help prevent issues related to software glitches or outdated firmware.

Tire Maintenance

Regularly checking tire wear and ensuring proper alignment can help prevent issues related to uneven tire wear caused by a malfunctioning Active Curve System.

GLE Coupé: ACTIVE CURVE SYSTEM >> Check out the video below:


The Active Curve System is an advanced suspension technology that enhances the driving experience for Mercedes-Benz owners.

However, malfunctions can occur and require professional diagnosis and repair. By recognizing the warning signs, seeking prompt assistance from a qualified technician, and performing regular preventative maintenance, drivers can help ensure the system continues to function optimally, providing a comfortable and stable driving experience.

Stephan K.

I have been working as a mechanic for over 13 years and have been deeper into advanced automotive diagnostics for some years.

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