Mercedes-Benz 300SEL Cruise Control Isn't Working

Common Causes of Cruise Control Malfunctions in Your Mercedes-Benz 300SEL and How to Fix Them

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Reviewed by
Devin Cabugcal
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 300SEL 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 300SEL 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.

Troubleshooting Cruise Control Issues in a Mercedes-Benz 300SEL

When troubleshooting cruise control issues in your Mercedes-Benz 300SEL, start with the basics to efficiently identify the problem. Begin by inspecting the fuse related to the cruise control system, as a blown fuse can easily disable the entire system. Next, check the brake light switch and the brake lights themselves; if the brake lights are malfunctioning, the cruise control may disengage unexpectedly, interpreting this as a signal that the brakes are being applied. If these components are functioning correctly, move on to the control module and the cruise control switch, ensuring they are operational. Additionally, examine the throttle actuation and linkage for any signs of wear or disconnection, as these mechanical elements are crucial for proper cruise control function. If the issue persists, consider the cruise control amplifier and actuator, as electronic failures in these parts can lead to intermittent operation or complete failure. By following this diagnostic approach, you can systematically narrow down the potential causes of your cruise control issues, making it easier to implement the necessary repairs.

What Are the Common Causes of Cruise Control Malfunctions in a Mercedes-Benz 300SEL?

When troubleshooting cruise control malfunctions in a Mercedes-Benz 300SEL, it's essential to understand the common problems that may arise within the system. One frequent issue is defective cruise control components, which can include the cruise control switch or module itself. Additionally, a faulty control stalk or an improper connection between the cruise control and the throttle body can disrupt functionality. Another critical factor to consider is the brake pedal switch; if this switch is defective, it may prevent the cruise control from engaging properly. Furthermore, a dead battery can also lead to cruise control issues, as it may not provide the necessary power for the system to operate. It's also worth checking the ABS wheel speed sensor, as a malfunction here can significantly impact cruise control performance. Lastly, engine or transmission problems, particularly in newer models, can cause the cruise control to disengage unexpectedly, especially if the engine light is illuminated. To effectively address these issues, a thorough visual inspection and testing of the relevant components are recommended, allowing for the identification and replacement of any faulty parts.

Why is the Cruise Control Not Working in a Mercedes-Benz 300SEL?

When the cruise control in your Mercedes-Benz 300SEL is not functioning, it is crucial to address the issue promptly, as neglecting it can lead to safety risks and potentially more significant vehicle problems. Common culprits include a defective brake pedal switch, which can prevent the system from engaging, or issues with the ABS wheel speed sensor and battery. Additionally, a blown fuse or problems within the throttle control system may also contribute to the malfunction. In older models, a broken vacuum line could be the source of the issue. It's essential to recognize that other factors, such as a faulty brake light or engine-related problems, can also impact cruise control functionality. Given the complexity of these systems, it is advisable to conduct a thorough inspection or consult a professional service team to accurately diagnose and resolve the problem, ensuring your vehicle remains safe and reliable on the road.

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