S5 Transmission Warning: Sluggish Shifts & Limp Mode Alert

Had similar transmission problems with my 2011 Audi S4. The automatic transmission symptoms matched exactly, sluggish shifting, unpredictable gear changes, and transmission warning lights. The root cause turned out to be an electrical undervoltage issue affecting the transmission control module. While transmission fluid condition was initially suspected, the diagnostic revealed the real problem was the voltage supply to the transmission control unit. The fix required: Full electronic diagnostic scan, Testing of the transmission control module, Replacement of a faulty voltage regulator, Recalibration of the transmission control unit This was a serious issue that could have led to complete transmission failure if left unaddressed. The slipping transmission symptoms improved immediately after the repair. The transmission performance returned to normal with smooth, predictable shifts. Important points: Get a proper diagnostic scan before assuming its transmission fluid, Check electrical system health, not just mechanical components, Have the transmission control module tested specifically, Ensure the shop has experience with Audi transmission problems The symptoms you describe are very similar to what happens with electrical issues affecting the transmission control systems. Would recommend finding a shop that specializes in European car transmission diagnostics.

Thanks for sharing your experience. Your case sounds really similar to mine. The electrical diagnosis path makes a lot of sense since I also noticed some erratic behavior from other electronics. Quick question, do you remember roughly how much the repair cost in total? Also curious if your automatic transmission has been running smoothly since the fix or if any other issues showed up? This really helped confirm I should focus on finding a shop with proper diagnostic equipment for transmission problems rather than rushing into a transmission flush or fluid change.

Just wanted to follow up that since fixing the undervoltage issue for 240 Euro, my transmission has been working flawlessly. The automatic transmission oil was worn out as initially suspected, but that was a separate maintenance item the mechanic addressed during the same visit. The car transmission now shifts perfectly, no more slipping transmission issues or warning lights. Its been 8 months of trouble-free driving since the repair. Getting proper electronic diagnostics really was key to solving the transmission problems correctly the first time. Having a mechanic with the right diagnostic equipment made all the difference in identifying both the electrical and hydraulic fluid issues. The transmission control module is working as intended now that its getting proper voltage. If your symptoms are truly similar, you should be looking at a comparable repair cost, though prices can vary. Just make sure they check both the electrical system and transmission fluid condition for a complete diagnosis.

I took my car to a specialized European auto shop last week after getting this helpful advice. The diagnostic testing confirmed it was indeed an electrical issue affecting the transmission control module, just like you experienced. The repair involved: Complete electronic diagnostic scan, Voltage regulator replacement, Fresh transmission fluid change, System recalibration Total cost came to 280 Euro and took about 4 hours to complete. The transmission problems cleared up immediately, no more warning lights or erratic shifting. The hydraulic fluid change was needed maintenance anyway, so I am glad they caught both issues. Really appreciate the guidance on finding a shop with proper diagnostic equipment for transmission problems. Saved me from potentially wasting money on unnecessary transmission work. The car drives like new again with smooth, predictable shifts. Will definitely stick with this mechanic for future transmission maintenance.