Audi S8 Cruise Control Failure, Common Fixes & Costs

I had a very similar issue with my Audi S7 from 2013. With some experience working on modern vehicles, I can share what worked in my case. The cruise control system stopped working entirely, and like yours, the throttle position was fine during manual driving. Initially thought it might be a blown fuse, but after checking the fuse box, everything was intact. Took it to my workshop where they diagnosed a faulty wiring connection between the steering wheel controls and the main control module. The cable had developed a poor connection over time, causing intermittent cruise control failures before completely failing. The repair involved replacing the damaged wiring harness and testing all connected components. Total cost was 95 Euro including diagnostics and labor. Since the fix, the cruise control has worked flawlessly. Could you share: Any dashboard light warnings? Does the cruise control button make any response at all? Have you noticed any other electrical issues? When did the problem first start, sudden or gradual failure? This info would help determine if your issue matches what I experienced or if it might be something different.

Thanks for sharing your experience. My Audi has 99767 KM and had its latest service 3 months ago. The dashboard light for cruise control only appears briefly when attempting to engage the system, then disappears without activation. The steering wheel controls seem to have power but produce no response when pressed. No other electrical issues noted. The failure happened gradually over about two weeks, starting with occasional non-engagement before failing completely. The throttle position sensor readings look normal in diagnostics, but there are multiple cruise control related fault codes stored in the system. Your wiring harness solution sounds promising, especially given the gradual failure pattern matches my situation. Will investigate the wiring connections before considering more expensive repairs.

Based on those additional details, it does sound remarkably similar to my experience. The gradual failure pattern and normal throttle position readings match exactly what happened with my S7. One thing I discovered during my repair was that the clock spring inside the steering wheel can also cause these symptoms. The intermittent engagement followed by complete failure is typical of clock spring deterioration. In my case, while the wiring harness was the primary issue, the technician found the clock spring was also showing early signs of wear. Given your mileage and the fact that the steering controls have power but no response, I would recommend having both the wiring harness and clock spring checked. The fault codes stored in the system should help pinpoint which component is causing the issue. My repair costs could have been higher if the clock spring needed replacement, but catching it early saved me from a more expensive fix later. If you need both components replaced, expect costs around 250-300 Euro compared to the 95 Euro I paid for just the wiring harness. Since your car recently had service, maybe check if the cruise control was working immediately after that service. Sometimes related components can be disturbed during routine maintenance.

Thanks everyone for the detailed responses. After reading through the suggestions, I checked my service records and noticed the cruise control was indeed working perfectly right after the last service. This timing detail plus the gradual failure pattern really points toward the wiring harness issue. I performed a basic inspection of the fuse box and verified the speed sensor connections, but found nothing obvious. The steering wheel controls still have power which supports the theory of a wiring connection problem rather than a complete system failure. Will schedule an appointment to have the wiring harness and clock spring checked since the symptoms match so closely with what others experienced. The expected repair cost of 250-300 Euro for both components seems reasonable compared to other potential fixes. Really appreciate the insights about checking both components together, as fixing just one might leave me with another failure soon after. Will update once the repair is completed to confirm if this resolved the cruise control issues.