Audi S3 Trans Sensor Failure Causing Erratic Shifts

I had a nearly identical issue with my 2020 S4 last winter. Having moderate experience working on cars, I first noticed similar symptoms, rough shifting and occasional grinding, followed by the transmission warning light. The transmission sensor was reporting incorrect readings, which caused transmission issues and eventually triggered limp mode. A workshop diagnostic revealed low transmission oil level was the root cause, which affected the transmission temperature sensor readings. The repair involved: Complete transmission oil level check, Transmission oil top-up, Sensor connection cleaning, Full diagnostic system reset Total cost was 365 Euro and the repair took about 3 hours. Since then, no more transmission issues or warning lights. Before suggesting specific fixes for your S3, could you share: Current mileage, Service history details, When was the last transmission oil change, Any modifications to the transmission system, Exact warning messages displayed This information would help determine if your issue matches what I experienced or if it might be something different requiring alternative solutions. Make sure to address this soon, as running with low transmission oil can lead to overheating problems and potentially severe transmission damage.

Latest transmission service was at 98000 KM, so fairly recent. I have kept up with all scheduled maintenance at authorized dealers. The warning message displays transmission malfunction with limp mode engaged. The troubling part is that these transmission issues started suddenly without any prior warning signs. I will definitely get it checked right away given the potential for transmission damage you mentioned.

Good to hear about your regular maintenance schedule. Based on my experience with the same issue on my S4, sudden transmission problems often point to sensor-related issues rather than mechanical failure, especially with well-maintained vehicles. When my gearbox sensor started acting up, it also happened without warning. The transmission oil temperature sensor can fail abruptly, causing the control unit to receive incorrect readings and trigger limp mode as a protective measure. While low transmission oil caused my problem, your symptoms, especially with recent service, strongly suggest an electrical issue with the sensor itself. The sudden onset matches exactly what happened with my car before the workshop diagnosed the faulty temperature sensor. A few things to consider: The gearbox sensor replacement cost me around 220 Euro plus labor, Repair time was roughly 2 hours, The fix completely resolved all overheating problems and warning lights One quick check you can do: monitor if the transmission behaves differently when the engine is cold versus fully warmed up. In my case, the faulty oil sensor caused more erratic shifting when warm, which helped confirm the diagnosis. Would recommend having the transmission control unit scanned for specific error codes to confirm if its indeed the sensor before any parts replacement.

Thanks for the detailed follow-up. Your mention of sensor-related transmission issues rather than mechanical failure gives me some hope. My car also shifts worse when warm, just like you described. My next step will be getting those error codes read. Since the transmission issues appeared so suddenly and the maintenance is up to date, focusing on the transmission oil temperature sensor seems like a logical starting point. The repair costs you mentioned, 220 Euro plus labor, sound reasonable compared to what I was worried about. I will schedule a diagnostic appointment this week. The fact that your similar symptoms were fully resolved after the gearbox sensor replacement is encouraging. Better to address these transmission problems now before they potentially lead to more serious damage.