Audi S5 Transmission Warning: Sensor vs Gearbox Issues

I had almost identical issues with my 2011 Audi S4 last year. I have some experience working on cars but automatic transmission problems are definitely workshop territory. The symptoms you describe match exactly what I experienced, rough gear shifting, warning lights, and transmission going into limp mode. My workshop first checked the gearbox oil level, which turned out to be significantly low. This can cause the temperature sensor to give false readings and trigger those exact symptoms. The repair involved: Full diagnosis of the automatic transmission system, Topping up the transmission fluid to correct level, Checking all gearbox sensors, Running computer diagnostics Total cost was 365 Euro and it completely resolved all the issues. The transmission has been shifting smoothly since then with no warning lights. Before suggesting more specific fixes, could you share: Current mileage on your S5? When was the last transmission fluid change? Are there any other warning lights on the dashboard? Does the problem occur more after the car has warmed up? This would help determine if your case might be similar or if there could be other underlying transmission repair needs.

Latest service was at 143000 KM, including an oil change and general inspection. The mechanic mentioned the transmission fluid looked good at that time. To answer your questions: The problem does seem to worsen after driving for about 15-20 minutes. The check engine light flashes occasionally along with the transmission warning. The temperature sensor reading fluctuates wildly on the display, which strengthens my suspicion about a faulty sensor. On particularly bad days, the transmission has trouble shifting between second and third gear. The grinding noise during gear shifting becomes more noticeable when the engine is warm. I am starting to think this might be more than just a temperature sensor issue and could require a more extensive transmission repair.

Thanks for the additional details. After hearing about the fluctuating temperature readings and the worsening symptoms when warm, this indeed sounds more complex than my initial case with the S4. The symptoms point toward potential transmission issues beyond just the sensor: Fluctuating temperature readings often indicate a failing transmission sensor, Grinding between 2nd and 3rd gear suggests mechanical wear, The combination of warning lights typically means multiple gearbox sensor inputs are affected In my case, I actually ended up needing more extensive repairs a few months after the initial fluid top-up. The overheating problems returned and the workshop found internal transmission wear causing the issues. The complete repair included: Replacement of the transmission temperature sensor, Valve body replacement, New transmission solenoids, Full transmission fluid flush Total cost was around 2800 Euro but solved all automatic transmission issues permanently. Given your symptoms are similar but more severe than my initial problems, I would recommend getting a full transmission diagnostic rather than just replacing the sensor. Would you be able to check if there are any metal particles in the transmission fluid? This was a key indicator in my case that helped identify the extent of internal wear.

Appreciate the detailed response and sharing your repair experience. This definitely helps put things in perspective, sounds like I might be facing a similar progression of transmission issues that you encountered. I checked the transmission fluid through the dipstick yesterday. While not obviously contaminated, there are some tiny metallic particles visible when wiping the dipstick on a white paper towel. This does make me concerned about internal wear in the automatic transmission, as you mentioned. Given the similarities with your case and the presence of metal particles, I will book a full transmission diagnostic rather than just assuming its a temperature sensor issue. The grinding noise and shifting problems definitely warrant a thorough check, especially since the symptoms get worse with heat. I will prepare for potential major transmission repair costs, though hoping it might still be caught early enough to avoid a complete rebuild. Thanks for sharing the cost breakdown of your repair, helps set realistic expectations. Will update once I get the workshop diagnosis.