1990 Audi 90 Cruise Control Isn't Working

Fixing Cruise Control Issues in the 1990 Audi 90

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Reviewed by
Andrew Hajjar
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 1990 Audi 90 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 1990 Audi 90 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.

What are the initial steps to diagnose the non-functional cruise control in a 1990 Audi 90?

When diagnosing the non-functional cruise control in a 1990 Audi 90, it's essential to adopt a systematic approach that prioritizes simpler checks before delving into more complex diagnostics. 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 explanation for the malfunction. Next, examine the cruise control switch located on the steering wheel; a faulty switch can prevent the system from engaging. Following this, check the vacuum hoses connected to the cruise control actuator for any signs of leaks or damage, as these can disrupt the system's operation. Additionally, testing the cruise control module is crucial to confirm that it is sending the correct signals. Finally, inspect the wiring throughout the cruise control system for any loose or disconnected connections that could be causing the issue. By methodically working through these steps, you can effectively diagnose the problem and determine the necessary repairs for your Audi's cruise control system.

What are the common problems that could cause the cruise control to stop working in a 1990 Audi 90?

When dealing with cruise control issues in a 1990 Audi 90, it's essential to understand the common problems that may be at play. One of the primary culprits is a faulty cruise control switch, which can prevent the system from engaging properly. Additionally, vacuum leaks within the cruise control system can lead to a loss of pressure, causing the system to malfunction. Another critical component to check is the speed sensor; if it is defective, it can disrupt the communication between the vehicle's speed and the cruise control, resulting in failure. It's also wise to inspect the fuses, as a blown fuse can halt the cruise control's operation entirely. Lastly, the brake light switch plays a vital role in cruise control functionality; if it is faulty, it may disengage the system unexpectedly. By systematically checking these components, DIYers can effectively troubleshoot and potentially resolve the cruise control issues in their Audi 90.

How urgent is it to address the malfunctioning cruise control in a 1990 Audi 90?

Addressing the malfunctioning cruise control in a 1990 Audi 90 is of utmost urgency due to the significant safety risks it poses. A malfunctioning system can lead to unexpected acceleration or deceleration, which can result in dangerous driving situations and increase the likelihood of accidents. Moreover, delaying repairs can exacerbate the problem, potentially causing further damage to the vehicle's components, leading to more extensive and costly repairs down the line. It is crucial for DIY enthusiasts to recognize these risks and prioritize the inspection and repair of the cruise control system. Taking prompt action not only ensures the safety of the driver and passengers but also helps maintain the overall integrity of the vehicle, making it essential to address any symptoms of malfunction without delay.

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1990 Audi 90 Cruise Control Issues & Repairs | RepairPal