Mercedes-Benz ML400 Cruise Control Isn't Working

Common Causes of Cruise Control Malfunctions in Your Mercedes-Benz ML400 and How to Fix Them

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Reviewed by
Bo Fader
Written by RepairPal Car Genius
Updated January 14, 2025
0%
30% chance it's the
Sensor
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25% chance it's the
Control Module
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25% chance it's the
Throttle
0%
20% chance it's
Something else
The most common reasons a Mercedes-Benz ML400 cruise control isn't working are failed control module, sensor or switch issues, or throttle actuation problems.
  • Sensor: A faulty or malfunctioning sensor can lead to incorrect readings, causing issues with engine performance or other systems relying on accurate data.
  • Control Module: A faulty control module can lead to erratic vehicle behavior or failure of various electronic systems due to improper signal processing.
  • Throttle: A faulty throttle body or a defective accelerator pedal position sensor may be causing inconsistent throttle response.
Proper diagnosis will determine the exact cause of your symptom, saving you money on unnecessary repairs. The diagnostic experts at RepairPal Certified shops have the right tools and experience to solve any symptom.

How much does it cost to fix a Mercedes-Benz ML400 cruise control isn't working?

Common Repairs

The total repair cost will vary based on the condition of your vehicle and the number of repairs needed to fix your symptom. Proper diagnosis will save you money by finding the exact repairs needed to fix your car right the first time.

In the event that a wheel speed sensor fails, the ABS, traction control system (TCS) and manufacturer specific stability control system lights will illuminate, informing the driver that the systems are disabled. The vehicle will be more prone to tire slip, and normal driving patterns may need to be adjusted to correct for the loss of computer control. On older vehicle's, the speedometer can be affected, causing illumination of the check engine light as well.

The cruise control switch can cause complete failure of the cruise control feature, but in a lucky scenario only partial functionality will be lost. This means that the cruise control may come on, but that it will not increase in speed automatically, or the cancel button does not work leading the driver to cancel cruise control with the foot brake. In some vehicles, the cruise control light may illuminate, or a warning message may be displayed due to lack of functionality.

Troubleshooting Cruise Control Issues in a Mercedes-Benz ML400

When troubleshooting cruise control issues in your Mercedes-Benz ML400, start with the simplest solutions first. Begin by checking the fuse related to the cruise control system, as a blown fuse can often be the culprit behind malfunctioning features. Next, inspect the brake light switch; if it’s faulty, it may prevent the cruise control from engaging. Additionally, ensure that the throttle is functioning correctly, as any actuation problems can disrupt the system. If these basic checks do not resolve the issue, consider examining the control module and associated sensors, as these components can fail and require replacement. Lastly, if the check engine light is illuminated, it’s crucial to address any underlying engine issues, as they can directly impact the cruise control functionality. By following this diagnostic approach, you can systematically identify the problem and determine whether a simple fix is possible or if professional assistance is needed.

What Could Cause the Cruise Control to Malfunction in a Mercedes-Benz ML400?

When diagnosing cruise control malfunctions in a Mercedes-Benz ML400, it's essential to consider several common problems that could be affecting the system. A failed control module, sensor, or switch is often at the root of these issues, particularly in older models like the 2004 ML350. Additionally, throttle actuation problems can disrupt the cruise control's functionality, making it crucial to inspect the throttle system for any irregularities. Another frequent culprit is a defective brake pedal switch, which can mislead the cruise control into thinking the brakes are engaged, thus disabling the system. Furthermore, issues with the ABS wheel speed sensor can also interfere with cruise control operations, as this sensor plays a vital role in maintaining speed. Lastly, problems with the brake light switch or malfunctioning brake lights can trick the cruise control into disengaging, leading to unexpected speed changes. Regular maintenance and immediate attention to warning signs can help ensure the cruise control system operates smoothly, allowing for a safer and more enjoyable driving experience.

Why is the Cruise Control Not Working in a Mercedes-Benz ML400?

When the cruise control in your Mercedes-Benz ML400 is not functioning, it is crucial to address the issue promptly, as neglecting it can lead to safety risks and further complications. A malfunctioning cruise control system may stem from a defective brake pedal switch, which is essential for the system's operation. Additionally, a dead battery can disrupt the electrical components necessary for cruise control to engage. If the ABS wheel speed sensor is faulty, it may not only affect cruise control but also trigger warning lights for the ESP and ABS systems, indicating a broader issue that could compromise vehicle safety. Furthermore, problems with the throttle control system or even a broken vacuum line in older models can exacerbate the situation. Ignoring these symptoms could lead to more significant damage and costly repairs down the line. Therefore, it is advisable to seek professional inspection and maintenance to ensure your vehicle remains safe and reliable on the road.

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