Audi A4 Cruise Control Failure: Diagnostic Tips

As someone with some experience working on Audis, I had a very similar issue with my 2013 Audi A6 last year. The cruise control malfunction was nearly identical, showing error messages in the instrument cluster and completely stopping functionality. After running car electronics diagnostics, it turned out to be a loose connection in the wiring harness leading to the steering wheel controls. The throttle body connections were initially suspected, but the real culprit was much simpler. The workshop found that some of the cruise control wiring had worked itself loose over time, causing intermittent connection issues. The fix was relatively straightforward and cost 95 Euro, mainly covering labor time to access and repair the connection. They also performed a full system reset after fixing the wiring to clear all error codes. To help diagnose your specific case, could you share: Have you noticed any other electrical issues recently? Does the steering wheel have any other malfunctioning buttons? Were there any specific events (like heavy rain or impacts) before the issue started? What exact error message appears in your cluster? This information would help determine if your A4 is experiencing the same connection issue or if its something else entirely.

After 149664 KM and my most recent service last month, I can confirm the faulty system started showing error codes for the cruise control. A quick check of the fuse box revealed no obvious issues. The steering wheel buttons still work fine except for the cruise control functions. The actuator seems to respond correctly when tested, but the malfunction persists. No water damage or recent impacts to report. The error message simply states cruise control unavailable. Looking forward to hearing if others faced similar issues with their A4s.

Based on your description and mileage, this sounds increasingly like the same issue I encountered with my A6. Since you mentioned the steering wheel buttons work except for cruise control, and the actuator tests fine, we might be looking at a different root cause than my initial wiring harness suggestion. After your response, I recalled another non-functional system issue I had at around 140000 KM, it turned out to be a faulty brake light switch. This switch is a critical safety component that needs to signal correctly for the cruise control to operate. The diagnostics initially masked this simple cause, leading to confusion about the actual problem. The repair cost in my case was about 85 Euro including the switch replacement and system reset. Much more affordable than initially feared when the malfunction first appeared. Consider having your workshop specifically check: Brake light switch functionality, Cruise control module connections, Ground wire integrity near the pedal assembly These components often show wear at similar mileage points and can trigger identical symptoms. The fact that your recent service didnt catch this suggests its likely a component that isnt typically inspected during routine maintenance.

Thanks for the additional insights. The brake light switch theory makes a lot of sense given my mileage and symptoms. Good to hear it might be a relatively simple and affordable fix rather than a major electronic malfunction. I called my regular workshop and they can check those specific components tomorrow. They mentioned they have seen several cases where the cruise control malfunction was indeed linked to the brake light switch, just as you described. The quoted inspection cost is 75 Euro, which seems reasonable to pinpoint the exact cause. I will update this thread once I get the car diagnosed properly. This information might help others who encounter similar cruise control issues with high-mileage vehicles. Having the steering wheel controls partially working while only the cruise control fails definitely points toward the brake switch as a likely culprit.