Audi Q8 Control Module Chaos: Multiple System Failures

As an A7 owner (2017 model with the 3.0T engine), I encountered nearly identical symptoms last year. The unusual electrical failures and warning lights pointed to a CAN bus communication issue, which the OBD-II scan confirmed with multiple malfunction indicator codes. The root cause was a damaged wiring harness where it connects to the main control unit. The connection had corroded and was intermittently losing contact with the BUS system. While the diagnostic process was straightforward, accessing the harness required removing several interior components. This is considered a serious electrical issue that should be addressed promptly, as it affects multiple vehicle systems and can potentially lead to safety-related malfunctions. The flickering engine diagnostics and unusual system shutdowns you describe are classic symptoms of a compromised BUS connection. The repair involved: Complete diagnostic scanning of all control modules, Removal of interior trim pieces, Replacement of the main harness connector, Testing all affected systems, Clearing stored error codes The service required about 6 hours of labor, but prevented potential damage to other electronic components. After the repair, all systems functioned normally with no recurring warning lights or communication errors.

Thanks for sharing your experience. Those symptoms do sound exactly like what I am dealing with in my Q8. My scan tool is also showing multiple communication errors across different modules. Really glad to hear you got it sorted with the wiring harness replacement. The warning lights and system shutdowns are driving me crazy so I want to get this fixed ASAP. Could you remember roughly what the total repair cost was? Also curious if you have had any other electrical issues pop up since the harness was replaced?

Wanted to follow up, got the repair done last week and it completely resolved those electrical gremlins in my Q8. The mechanic found exactly what was suspected, a faulty cable connection at the control module causing communication issues with the BUS system. The repair costs came to 155 Euro which included the diagnostic work and fixing the connection. Since the repair, the malfunction indicator lights have stayed off and all systems are working perfectly. No more unusual warning lights or system failures with the radio, nav, or other modules. The service required was relatively quick once they identified the exact connection point that was causing the communication breakdown. Much simpler fix than initially feared and definitely worth getting done to prevent further electrical issues. The symptoms you described match exactly what I experienced, so hopefully this helps confirm you are on the right track. Getting those control module connection issues fixed promptly is important to avoid any cascade of electrical problems.

Thanks all for the advice. Took my Q8 to a repair shop that specializes in electrical issues. The mechanic spotted the failing connector right away during the diagnostic scan. Really glad I got a second opinion. The service required was straightforward once they knew what to look for. They found corrosion on the main harness connector causing all those unusual warning signals and system failures. Total repair came to 890 Euro including parts and labor, but worth every cent to have my car working properly again. The check engine light has stayed off and all control modules are working perfectly for the past week. No more unusual shutdowns or electrical glitches. The OBD-II scan is now clear of any error codes. Such a relief to have this fixed properly instead of getting the runaround from that first shop. Definitely learned my lesson about finding a qualified mechanic for electrical issues. The malfunction indicator symptoms were spot on to what others described here. Thanks again for helping me avoid getting ripped off.