Mercedes-Benz SL400 Cruise Control Isn't Working

Common Causes of Cruise Control Malfunctions in Your Mercedes-Benz SL400 and How to Fix Them

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Reviewed by
Aisha
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
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20% chance it's
Something else
The most common reasons a Mercedes-Benz SL400 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 SL400 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.

A faulty cruise control module will simply result in deactivation of cruise control settings. This is because a detected error in the cruise control system could lead to hazardous driving conditions, so the module will be disabled, and the cruise control system warning light will be displayed. This will be a different message depending on make and model, and a warning light or message may be displayed on the driver instrument cluster.

Troubleshooting Cruise Control Issues in a Mercedes-Benz SL400

When addressing cruise control issues in your Mercedes-Benz SL400, start with the simplest potential problems before delving into more complex diagnostics. Begin by checking the fuse associated with the cruise control system, as a blown fuse can easily disrupt functionality. Next, inspect the brake light switch; if it is faulty, it may prevent the cruise control from engaging. Additionally, ensure that the brake lights are functioning properly, as any malfunction here can signal to the system that the brakes are applied, thus disabling cruise control. If these basic checks do not resolve the issue, turn your attention to the control module and sensors, as failures in these components can lead to more significant problems. Pay attention to any warning messages displayed on the instrument cluster, as they can provide clues about the underlying issue. If the cruise control intermittently drops out while driving, consider potential throttle actuation problems, which may require more in-depth diagnostics. While DIY troubleshooting can be effective, remember that consulting the operator's manual for your SL400 can offer specific guidance tailored to your vehicle, and seeking professional assistance may be necessary for a thorough diagnosis and repair.

Troubleshooting Cruise Control Issues in a Mercedes-Benz SL400

When troubleshooting cruise control issues in your Mercedes-Benz SL400, it's essential to understand the common problems that may arise. One frequent culprit is a failed control module, sensor, or switch, which can disrupt the system's functionality. Additionally, throttle actuation problems can prevent the cruise control from engaging properly. It's also important to check for a blown fuse, as well as the condition of the brake light and brake switch, since these components play a crucial role in the cruise control operation. If you notice that the cruise control intermittently drops out while driving, this could indicate underlying electronic or mechanical issues that need attention. Furthermore, the presence of a check engine light may signal engine-related problems that could affect the cruise control system. For a thorough diagnosis, refer to your operator's manual for specific troubleshooting steps, and consider consulting with a professional if the issues persist, ensuring your cruise control system is restored to optimal performance.

Why is the Cruise Control Not Working in a Mercedes-Benz SL400?

When the cruise control in your Mercedes-Benz SL400 is malfunctioning, it is crucial to address the issue without delay. Ignoring symptoms such as intermittent operation or complete failure can lead to significant safety risks, particularly during long drives where maintaining a consistent speed is essential. Problems like mismatched tire sizes or uneven wear can not only disrupt cruise control functionality but also affect overall vehicle handling. Additionally, a faulty ABS sensor can disable critical safety systems, including ABS and stability control, increasing the risk of accidents. A defective brake pedal switch or blown fuse may seem minor, but they can lead to unexpected disengagement of cruise control, which could be dangerous in high-speed situations. Furthermore, issues with the throttle control system or a damaged speed sensor can prevent the cruise control from engaging properly, potentially resulting in erratic vehicle behavior. Therefore, it is advisable to diagnose and resolve these issues promptly to ensure your vehicle operates safely and efficiently.

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