Audi 100 Quattro Cruise Control Isn't Working

Common Causes of Cruise Control Malfunctions in Your Audi 100 Quattro 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 Audi 100 Quattro 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 Audi 100 Quattro 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.

Troubleshooting Cruise Control Issues in an Audi 100 Quattro

When troubleshooting cruise control issues in your Audi 100 Quattro, it's essential to adopt a systematic diagnostic approach. Start by checking the basic connections and voltages; this involves measuring the ohms on specific connections to confirm they are functioning correctly. Next, access the cruise control stalk by unscrewing the two screws that secure the 6-pin housing, allowing you to follow the test procedures for a more detailed diagnosis. It's also crucial to locate the cruise control module, which is often found under the hood, as this component can be a common source of problems. As you investigate, consider examining other related parts such as the control module, throttle, and sensors, as these can also contribute to cruise control malfunctions. If your cruise control has suddenly stopped working, methodically follow the troubleshooting steps to identify the issue before seeking professional assistance. Additionally, be aware that if your vehicle is equipped with adaptive cruise control, you may need to inspect outer sensors and cameras that assist with various driving functions. By following this structured approach, you can effectively diagnose and potentially resolve cruise control issues in your Audi 100 Quattro, saving time and money in the process.

What Could Cause the Cruise Control to Malfunction in an Audi 100 Quattro?

When diagnosing cruise control malfunctions in an Audi 100 Quattro, it's crucial to consider several common problems that could be affecting the system. A blown fuse is often the first culprit to check, as it can interrupt power to vital components like the cruise control switch and the vehicle speed sensor. Additionally, a defective brake pedal switch can prevent the cruise control from engaging, as it signals the system to deactivate when the brakes are applied. Issues with the throttle control system may also arise, leading to erratic behavior or complete failure of the cruise control. Furthermore, problems with the Anti-lock Braking System (ABS) can interfere with cruise control functionality, as these systems are interconnected. In older models, a broken vacuum line can be a frequent issue, disrupting the vacuum-operated cruise control mechanism. Lastly, a faulty control module or other electrical connections can lead to persistent problems. By systematically checking these components, DIYers can effectively identify and resolve the underlying issues causing cruise control malfunctions in their Audi 100 Quattro.

Why is the Cruise Control Not Working in an Audi 100 Quattro?

When the cruise control in your Audi 100 Quattro fails, it’s crucial to address the issue promptly, as neglecting it can lead to safety risks and further complications. A blown fuse is often the first suspect, as it serves as a protective measure against electrical faults. Additionally, a defective brake pedal switch can prevent the cruise control from engaging, as it is responsible for signaling when the brakes are applied. Problems with the throttle control system or the Anti-lock Braking System (ABS) can also disrupt cruise control functionality, potentially leading to erratic vehicle behavior. In older models, a broken vacuum line may be the culprit, while a malfunctioning vehicle speed sensor can hinder the system's ability to maintain speed accurately. Lastly, a faulty control module can completely disable the cruise control feature. Given the potential for these issues to affect your driving experience and safety, it is advisable to diagnose and resolve the underlying problems as soon as possible to restore the functionality of your cruise control system.

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