A5 Transmission Nightmare: Emergency Mode Alert

I had a similar issue with a 2021 A4 with the automatic transmission showing those exact symptoms. Having some experience working with modern transmissions, I recognized this could be either mechanical or electrical. Took it to the workshop where they diagnosed an undervoltage problem affecting the transmission control unit. The slipping transmission symptoms and emergency mode were actually triggered by the electrical system, not by the hydraulic fluid or mechanical components. The repair cost 240 Euro and included: Full diagnostic scan, Testing of the electrical system, Repair of a faulty voltage regulator, System reset and adaptation The transmission flush and fluid weren't the issue at all, it turned out the transmission control unit wasn't getting stable power, causing erratic shifting patterns. To better assist with your A5 situation, could you share: Current mileage, When the symptoms first appeared, If any other electrical issues occurred, Whether the battery has been replaced recently, If any aftermarket electronics were installed These details would help determine if you're facing a similar electrical problem affecting your transmission performance.

Thanks for the detailed reply about the electrical issues. My A5 has 158213 KM on the clock from regular commuting, last serviced 3 months ago. No aftermarket electronics installed and battery is factory original. The automatic transmission problems started suddenly last week, no warning signs before the emergency mode kicked in. No other electrical issues noticed. The transmission performance declined rapidly after that first incident. Interesting that your case was voltage-related rather than fluid. Will definitely have them check the electrical system when I take it in. The symptoms match exactly what you described with the slipping transmission behavior. Worth noting that despite the high mileage, transmission fluid has never been changed since its new. Maybe worth doing a transmission flush while they diagnose the electrical system, just to rule that out completely.

As mentioned in my previous reply, I fixed a very similar issue on my A4, and your latest details actually strengthen my suspicion about electrical problems. The factory original battery at that mileage could definitely be the root cause of the transmission performance issues. The high mileage combined with an original battery is concerning. A weakening battery can cause voltage fluctuations that directly impact the automatic gearbox control unit, triggering those exact symptoms you described. While a transmission flush might seem logical, I would actually recommend this approach: First get the battery tested and electrical system diagnosed, Have them check voltage stability at the transmission control unit, Only consider a transmission oil change if electrical tests come back normal In my case, investing in the electrical diagnosis first saved me from an unnecessary transmission service. The automatic transmission returned to normal shifting immediately after fixing the voltage issue. The sudden onset of symptoms without warning also matches the electrical theory rather than fluid degradation, which typically shows gradual performance decline. Would suggest getting this checked soon, as voltage issues can potentially damage the transmission control unit if left unaddressed for too long.

Thanks for breaking down the electrical diagnosis angle, this makes a lot of sense given how suddenly my transmission issues appeared. You raised good points about the original battery potentially causing problems at this mileage. After hearing about your experience, I scheduled an appointment to have the electrical system checked first before jumping into any transmission oil service. The car transmission symptoms do match what you described with the voltage problems, especially how quickly everything deteriorated after that first incident. Since my battery is the original one after 158213 KM, starting with electrical diagnosis seems like the smart approach. The slipping transmission could well be a symptom rather than the core issue. Really helpful to know that fixing your voltage problem immediately restored normal shifting without needing hydraulic fluid work. Will update once I get the results from the diagnostic tests. Hoping its just a voltage issue like in your case rather than internal transmission problems. The workshop said they can check everything next week, so fingers crossed for a straightforward fix.