Audi Q5 Cruise Control Failure: Common Sensor Issue

Had almost the same issue with my 2012 Audi Q3 last year. Have some experience working on basic car electronics, but this one needed professional help. The cruise control stopped working suddenly during a drive. Like yours, the car ran fine otherwise. After checking the basic stuff like the brake light switch and blown fuse connections myself, I took it to a workshop. Turned out the issue was a damaged wiring harness connector going to the pedal switch. The technician found that moisture had gotten into the plug connection, causing corrosion. They cleaned the connections and replaced the damaged part of the wiring harness. Total repair cost was 95 Euro and fixed the problem completely. Could definitely be a similar issue with your Q5, but would need to know: Are there any other warning lights on the dash? Does the brake light work normally? When you press the cruise control buttons, does anything show up on the display at all? The throttle position sensor could also be the culprit, but usually that would cause other drivability issues too. These systems are pretty interconnected, so getting a proper diagnostic scan would be the best first step.

Had the car serviced just 2 weeks ago at 20930 KM, so all regular maintenance is up to date. The brake lights work perfectly and no other warning lights appear on the dash. When pressing the cruise control buttons, absolutely nothing shows on the display. Previously it would at least flash briefly. Based on your experience, I will have the wiring checked. Seems the speed sensor connections and clock spring assembly should also be inspected since those can cause similar symptoms. The fuse box showed no obvious issues when I checked. Will book it in for a proper diagnostic scan to pinpoint the exact cause. Thanks for the detailed feedback about the wiring harness, that gives me a good starting point to discuss with the mechanic.

Thanks for providing those additional details. Since you mentioned having similar symptoms to my Q3, the complete lack of display response when pressing the cruise control buttons matches exactly what I experienced. While the wiring harness was the culprit in my case, the fact that yours stopped showing even the brief display flash is interesting. This often points to either a complete break in the signal path or a failed clock spring in the steering wheel, which carries the cruise control button signals. After my repair, I learned these systems typically fail in a predictable sequence: 1. Intermittent operation 2. Brief display flashes 3. Complete system shutdown Since you had normal operation until a sudden complete failure with no display response, I would actually suggest having them check the clock spring first. Mine showed similar symptoms when it first started acting up, but I caught the wiring issue before total failure. The dashboard light for cruise control staying completely dark, combined with working brake lights and no other warning indicators, really does mirror the early stages of my problem. If they find the wiring and clock spring are good, the next step would be checking the throttle position sensor connections. A proper diagnostic scan should quickly identify if its following the same pattern as my repair. The scan tool will show if its a signal interruption like mine or a component failure.

Based on your experience, I will have it checked out tomorrow. When you mentioned the typical failure sequence, it matches what happened, it worked fine one day and completely died the next with no warning or intermittent issues first. The mechanic should definitely inspect both the wiring harness and clock spring assembly since either could cause this type of sudden failure. No point replacing parts out of nowhere when a proper diagnostic scan can pinpoint the exact issue. The steering wheel and cruise control buttons themselves look perfectly normal, but clearly something is interrupting the signals. The speed sensor connections are worth checking too, but since the speedometer works correctly, that seems less likely to be the problem. At least the fuse box inspection ruled out the simplest potential fix. Really appreciate you sharing your repair experience in detail. Having this information will help ensure the mechanic checks all the common failure points. Will update once I know what was actually causing the problem in my case.