Mercedes-Benz S420 Cruise Control Isn't Working

Common Causes of Cruise Control Malfunctions in Your Mercedes-Benz S420 and How to Fix Them

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Reviewed by
Andrew Hajjar
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 S420 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 S420 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 S420

When troubleshooting cruise control issues in your Mercedes-Benz S420, start with the simplest potential problems before moving on to more complex diagnostics. Begin by checking the brake pedal switch, as a defective switch can easily disrupt the cruise control system. Next, inspect the fuses related to the cruise control; a blown fuse can prevent the system from functioning altogether. If these initial checks do not resolve the issue, examine the throttle actuation and ensure that the control module and sensors are functioning correctly. Pay attention to any warning lights on your dashboard, such as those for the ABS or ESP systems, as they may indicate underlying issues that could affect cruise control performance. If the problem persists, it may be necessary to consult a professional service team, as diagnosing electronic and mechanical components often requires specialized tools and expertise. By following this methodical approach, you can effectively identify and address the root cause of your cruise control problems.

What Could Cause the Cruise Control to Malfunction in a Mercedes-Benz S420?

When dealing with cruise control malfunctions in a Mercedes-Benz S420, it's essential to recognize the common problems that may arise. One frequent issue is the failure of key components such as the control module, throttle, or cruise control switch, which can disrupt the system's functionality. Additionally, electrical problems, including a dead battery or blown fuses, can prevent the cruise control from engaging properly. It's also important to consider the brake pedal switch, as a defect here can inadvertently disable the cruise control. For those looking to diagnose the issue themselves, conducting a diagnostic test can be invaluable in pinpointing the exact cause of the malfunction. Furthermore, the ASR II system, which integrates various electronic and hydraulic components, may also contribute to cruise control problems. Lastly, older systems may experience issues with broken vacuum lines or speed sensor malfunctions, which are common culprits in cruise control failures. By understanding these potential issues, DIYers can take informed steps toward troubleshooting and fixing their cruise control system.

Why is the Cruise Control Not Working in a Mercedes-Benz S420?

When the cruise control in your Mercedes-Benz S420 fails to operate, it is crucial to address the issue promptly, as neglecting it can lead to significant safety risks and potential vehicle damage. A malfunctioning cruise control system may stem from various causes, such as a defective brake pedal switch or a dead battery, which can compromise your ability to maintain control over the vehicle during long drives. Additionally, issues with the ABS wheel speed sensor or throttle control system can further exacerbate the problem, leading to erratic vehicle behavior. Ignoring these symptoms not only affects your driving experience but can also result in costly repairs down the line. Therefore, if you notice any signs of cruise control malfunction, it is advisable to seek professional inspection and repair to ensure your vehicle remains safe and reliable on the road.

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