S6 No-Start Mystery: Ignition Circuit Failure Fix Needed

Had a similar issue with my 2016 S4. The symptoms match exactly, complete silence when turning the key, no electrical response, throwing ignition circuit codes. The root cause was a combination of problems in the power supply system. The wiring harness connecting to the starter solenoid had deteriorated, creating an intermittent circuit break. The ignition switch itself was also showing signs of internal wear. The repair required: Complete diagnostic of the electrical system, Replacement of the ignition switch assembly, Rewiring the starter solenoid connection, Testing all related circuit connections This was classified as a serious electrical system issue that could have left the car stranded at any time. The complete lack of response when turning the key is a telltale sign of either the ignition switch failing or a break in the circuit between the switch and starter components. Would strongly suggest having a specialized electrical diagnostic performed, focusing specifically on the ignition switch and associated wiring harness. The zero response symptoms typically point to a complete circuit failure rather than a partial component issue.

Thanks for sharing your experience with the S4. Seems like we had very similar issues. After reading your reply, I checked the battery terminals and relay switch as well, but those were fine. Finally took it to a different shop that specializes in Audi electrical systems and they found almost the exact same problems you described, bad wiring harness and worn ignition switch. Can you recall roughly how much the total repair cost in your case? Also curious if youve had any other electrical gremlins pop up since getting it fixed? Looking to know what to expect in terms of future issues.

Great to hear you got the Terminal 15 ignition positive issue sorted. My repair ended up being similar but a bit more extensive than yours. The shop charged me around 850 Euro total since they had to replace both the wiring harness and deal with a voltage drop issue in the starter circuit. Sounds like you got a much better deal at 95 Euro with just the cable connection requiring attention. A bad connection at the terminal can definitely cause those no-start symptoms, so that tracks with what they found. Since getting it fixed over a year ago, the electrical system has been rock solid. No more issues with the starter solenoid or any other ignition-related problems. The key turns and the car fires up perfectly every time now. The specialized shop definitely made the difference in properly diagnosing the exact connection issue rather than just throwing parts at the problem. When these ignition circuit issues pop up, having someone who knows how to trace the power flow through the system is crucial.

After dealing with this frustrating no-start situation, I finally got it resolved. Based on the advice here, I took it to an electrical specialist who actually knew what they were doing. The total repair came to 780 Euro, they found a failing ignition switch and damaged wiring harness just like others mentioned. The power supply system needed a complete overhaul. They had to replace the entire wiring harness and install a new ignition switch assembly. Once they got everything connected properly, the car fired right up. Its been running perfectly for the past two weeks with no sign of any electrical issues. What really gets me is the first shop charged 400 Euro just to tell me they couldnt find the problem. The specialist did a proper diagnostic of the car wont start condition and found the exact issue within an hour. Definitely learned my lesson about going to shops that specialize in electrical problems rather than general mechanics when dealing with complex ignition circuit issues. Really glad I asked here before spending more money at the wrong place. The car starts perfectly now, no more turning the key to silence.