Audi A3 Transmission Warning Signs Point to Sensor Issue

Had a very similar transmission issue with my 2019 Audi A4. As someone with moderate experience in car maintenance, I initially thought it was a major transmission repair coming up when the gear shifting became rough and warning lights appeared. After taking it to a workshop, they diagnosed low transmission fluid as the root cause, which was causing the transmission sensor to give faulty readings and trigger the emergency mode. The automatic transmission was struggling due to insufficient lubrication, leading to those grinding sounds you mentioned. The fix involved a complete transmission fluid change and system inspection, costing 365 Euro. They found a small leak that was causing the fluid loss. The repair took about 4 hours, and the transmission issues completely disappeared after that. Before jumping to major transmission repair conclusions, it would help to know: Current mileage on your A3? When was the last transmission fluid change? Are you noticing any fluid spots where you park? Does the transmission issue occur more when the engine is cold or warm? The symptoms you describe match my experience, but transmission issues can have multiple causes. Getting these details would help narrow down if your problem is similar to what I encountered.

Thanks for sharing your experience. My A3 has 89309 KM and last had transmission oil changed during routine service 6 months ago. The symptoms in my case seem more severe than just low fluid levels. When checking underneath, no visible leaks or spots appear where I park. The transmission issues occur mainly after the car warms up, especially during highway driving. The gear shifting problems and grinding sounds typically start after about 15-20 minutes of driving. The transmission sensor warnings appear consistently at this point, suggesting the temperature-related issues are getting worse with engine heat. Based on the workshop diagnosis and these patterns, it seems the faulty gearbox sensor is the likely culprit rather than fluid levels.

Thanks for those additional details about your A3. The symptoms you describe actually differ from my A4 case, and I agree it sounds more like a sensor-related issue rather than fluid levels. After your response, I recalled that my A4 had a second transmission issue 6 months later that matches your symptoms more closely. The transmission sensor was indeed faulty, causing similar problems with gear shifting and warning lights after warm-up. The gearbox sensor failure caused incorrect temperature readings, making the transmission control unit think it was overheating. This triggered the emergency mode as a protective measure. The grinding noise during gear shifting happened because the transmission was operating with incorrect pressure settings based on false temperature data. The repair involved replacing the transmission oil temperature sensor and recalibrating the control unit. Total cost was around 450 Euro, mainly for the sensor unit and programming. The work took about 3 hours, significantly less time than a major transmission repair. Since your symptoms appear mainly after warming up and during highway driving, this strongly suggests a faulty sensor rather than mechanical transmission issues. A transmission repair specialist should be able to confirm this with diagnostic testing.

I appreciate everyone's detailed feedback. After comparing my symptoms with others' experiences, particularly the second case involving the faulty gearbox sensor, I feel more confident about the diagnosis. The overheating problems and transmission issues following a specific warm-up period match exactly what others have described. The temperature sensor failing seems to be a common problem that triggers these exact symptoms, rough shifting, warning lights, and emergency mode activation. I will proceed with the workshop's recommendation to replace the transmission sensor. The quoted repair cost of 480 Euro and estimated 3-4 hour job time aligns with what others paid for similar fixes. This seems much more reasonable than a complete transmission overhaul. The feedback here has been valuable in confirming that the transmission oil temperature readings are likely incorrect due to the faulty sensor, rather than actual mechanical problems. Will update once the repair is completed to confirm if this resolves the overheating problems and transmission warning lights.