BMW 840Ci Cruise Control Isn't Working

Common Causes of Cruise Control Malfunctions in Your BMW 840Ci 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
0%
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 BMW 840Ci 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 BMW 840Ci 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.

When the throttle position sensor fails, the engine's computer tends to overcompensate with fuel, leading black exhaust coming from the tailpipe. There is a strong possibility of engine misfires, and the check engine light will come on.

Throttle position sensors can also develop "dead spots," or certain places along the throttle curve where it doesn't get a reading. When this happens, the above symptoms can occur but then stop when you further press or let off the gas pedal.

When the vehicle speed sensor fails or the wiring harness prevents signal transmission, the speedometer is the first thing that will stop functioning properly. This can be an intermittent issue where the speedometer only works occasionally, the speedometer may cease all function, or the speedometer may read erratically or incorrectly. Also, the traction control and anti lock brake warning lights specific to each vehicle may be illuminated, depending on the design of those systems. You may notice the vehicle hesitate to accelerate, cruise control will not function properly, and the vehicle may not shift properly through all of the gears.

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 BMW 840Ci

When troubleshooting cruise control issues in your BMW 840Ci, it's essential to adopt a systematic diagnostic approach. Start by checking the simplest components, such as the vehicle's fuse box, to see if a blown fuse is the culprit. If the cruise control fuse appears damaged, replacing it could resolve the issue. Next, inspect the battery and wiring for any signs of corrosion or damage, as these can disrupt the electrical flow necessary for cruise control functionality. Pay particular attention to the speed sensor, as dirt or malfunction can lead to erratic behavior. If these initial checks do not yield results, delve deeper into the throttle control system, looking for any obstructions or wear that might affect actuation. Additionally, be aware of potential intermittent issues, such as faulty solder joints or broken gears within the cruise control actuator, which may require more advanced repairs. By following this structured approach, you can effectively diagnose and potentially fix cruise control problems in your BMW 840Ci, saving time and money while enhancing your DIY skills.

What Could Cause the Cruise Control to Malfunction in a BMW 840Ci?

When dealing with cruise control malfunctions in a BMW 840Ci, 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 issues can prevent the cruise control from engaging properly. Dirty or malfunctioning sensors, particularly speed sensors, can also hinder communication with the vehicle's computer, leading to erratic behavior. In some cases, a bad solder joint in the cruise control actuator may cause intermittent failures, especially in warmer conditions. Drivers may notice random shutdowns of the system during highway driving, often requiring a simple restart of the vehicle to regain functionality. To effectively diagnose these issues, it's advisable to check the ABS control module and wheel speed sensors using a multi-meter for diode and resistance tests. By understanding these common problems, DIYers can take the necessary steps to troubleshoot and potentially resolve cruise control issues in their BMW 840Ci.

Why is it Urgent to Fix the Cruise Control in a BMW 840Ci?

Addressing cruise control problems in a BMW 840Ci is not just a matter of convenience; it is a pressing safety concern that demands immediate attention. A malfunctioning cruise control system can lead to unpredictable speed changes, increasing the risk of accidents on the road. Moreover, performance issues stemming from faulty components can compromise the vehicle's overall efficiency, affecting fuel consumption and engine responsiveness. Legal compliance is another critical factor, as driving with known mechanical issues can result in penalties in certain jurisdictions. Beyond safety and legality, a properly functioning cruise control system enhances the driving experience, particularly during long journeys, by reducing fatigue and improving comfort. Ignoring these issues can lead to more severe and costly repairs in the future, making it essential to address any cruise control malfunctions promptly. In summary, the urgency of fixing the cruise control in a BMW 840Ci is underscored by the need to ensure safety, maintain vehicle performance, comply with regulations, enhance driving comfort, and prevent further mechanical damage.

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