RS3 No-Start: Ignition Switch Circuit Power Loss Fix

Having dealt with a similar starting issue on my 2016 S3, I can share some relevant experience as someone with moderate car repair knowledge. The symptoms you describe match exactly what I encountered, no power to the starter solenoid despite good battery and fuses. After checking the fuse box thoroughly, my workshop discovered a damaged wire connection at the relay switch controlling the ignition circuit. When my car won't start, it showed similar error codes. The fix involved: Complete circuit break testing, Replacing corroded connector terminals, Installing a new relay switch assembly, Rechecking all ground connections Total repair cost was 95 Euro including diagnostics and parts. Before suggesting specific fixes, could you please share: Complete error codes from diagnostics, Whether the instrument cluster powers up normally, If you hear any clicking from the starter when turning the key, Whether this started happening suddenly or gradually This would help determine if your issue matches what I experienced or if it might be something else in the starting circuit. Remember to have a professional check the starter solenoid connections, as DIY diagnostics of the ignition system can be tricky without proper testing equipment.

Thanks for the helpful suggestions. My Audi just had its 15000km service last month, currently at 17020km. After testing the wiring harness connections as suggested, I discovered corrosion on the main ground wire near the starter. Getting this replaced tomorrow at the shop since I would rather not risk damaging other electrical components by continuing to drive it. Will update once fixed.

Thanks for the update on your RS3. Smart move checking those ground connections, corroded grounds often cause voltage drop issues that can trick us into thinking it's the terminal 15 circuit. Had the exact same problem around 16000km on my S3, and replacing that ground wire near the starter solenoid fixed it completely. Just keep in mind to have them check the other ground points while they're at it. When one connection starts corroding, others might follow soon. In my case, they found two other spots starting to show early signs of corrosion in the fuse box area. Would be great if you could share an update after the repair. It'll help confirm if we're dealing with the same underlying issue that affected several cars in this model range. Tip based on my experience: Once fixed, spray the new connections with contact cleaner and protectant to prevent future corrosion. This helped me avoid any repeat issues with my car won't start situations.

Thanks for the guidance. Quick update: The shop replaced the corroded ground wire today for 85 Euro and the car starts perfectly now. They also cleaned and protected all other ground connections as suggested. Found some minor corrosion starting on two other ground points, so catching this early probably prevented bigger issues. The voltage drop was indeed caused by the bad ground connection, running a circuit break test confirmed this was the only problem area. My car won't start issues are completely resolved. Good lesson learned about checking ground connections first before assuming more complex problems with the power supply system. Will definitely keep an eye on those terminals during future maintenance.