1991 Mercedes-Benz 300E Cruise Control Isn't Working

Fixing Cruise Control Issues in Your 1991 Mercedes-Benz 300E

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Reviewed by
Aisha
Written by RepairPal Car Genius
Updated January 14, 2025
0%
30% chance it's the
Sensor
0%
25% chance it's the
Control Module
0%
25% chance it's the
Throttle
0%
20% chance it's
Something else
The most common reasons a 1991 Mercedes-Benz 300E 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 1991 Mercedes-Benz 300E 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.

What are the initial diagnostic steps to troubleshoot the non-functional cruise control in a 1991 Mercedes-Benz 300E?

When troubleshooting the non-functional cruise control in a 1991 Mercedes-Benz 300E, it's essential to adopt a systematic diagnostic approach that prioritizes simpler checks before delving into more complex issues. Start by inspecting the fuse box to ensure that the fuse associated with the cruise control system is intact, as a blown fuse can often be the simplest fix. Next, examine the cruise control switch located on the steering wheel to confirm it is operational, as a malfunctioning switch can prevent the system from engaging. Following this, assess the cruise control module for any signs of failure, as this component is crucial for the system's functionality. Additionally, inspect the vacuum lines for any leaks or damage, as these can significantly impact the system's performance. It's also important to test the brake pedal switch, ensuring it is not stuck or faulty, since this can interrupt the cruise control operation. Lastly, verify the vehicle speed sensor to ensure it is accurately relaying information to the cruise control system. By methodically working through these steps, you can effectively identify and address the issues affecting your cruise control system.

What are the common problems that could cause the cruise control to stop working in a 1991 Mercedes-Benz 300E?

When dealing with a malfunctioning cruise control system in a 1991 Mercedes-Benz 300E, it's essential to understand the common problems that may be at play. One of the first areas to check is the cruise control switch, as a faulty switch can prevent the system from engaging. Additionally, the brake light switch plays a crucial role; if it is defective, it may inadvertently signal the cruise control to disengage whenever the brakes are applied. Another potential culprit is vacuum leaks within the cruise control system, which can lead to a loss of pressure and functionality. The speed sensor is also vital, as a malfunction here can hinder the system's ability to maintain the desired speed. Don't overlook the possibility of a blown fuse, which can cut power to the cruise control circuit entirely. Lastly, inspect the throttle cable for any signs of wear or damage, as issues with this component can affect the system's performance. By systematically checking these components, you can effectively diagnose and address the cruise control issues in your vehicle.

How urgent is it to repair the non-functioning cruise control in a 1991 Mercedes-Benz 300E?

When evaluating the urgency of repairing the non-functioning cruise control in your 1991 Mercedes-Benz 300E, it's essential to weigh the potential consequences of neglecting this issue. While cruise control is primarily a convenience feature, its malfunction can lead to increased driver fatigue during long trips, which may compromise safety. If the system's failure affects your ability to maintain a steady speed or distracts you while driving, addressing the repair becomes more pressing. Additionally, if you rely heavily on cruise control for comfort during your commutes, the inconvenience of its malfunction may prompt you to prioritize the repair. Furthermore, from a resale perspective, a fully functional cruise control system can enhance your vehicle's appeal and value, making it a worthwhile investment. Ultimately, consulting with a mechanic can provide clarity on the specific issues at hand and help you determine the best course of action based on your driving habits and safety considerations.

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