VW Caddy Auto Trans Issues, Fluid Problems or More?

I had a similar transmission performance issue with my VW Golf 2019 automatic. Given my moderate experience with transmission problems, I can share what worked in my case. The symptoms were quite similar, unpredictable shifting and transmission warning lights. Initially thought it was transmission fluid related too, but the workshop diagnosed an undervoltage issue affecting the transmission control unit. The low voltage was causing the transmission to enter a safety mode, which explained the erratic shifting patterns. The fix involved: Testing the battery and charging system, Replacing a faulty voltage regulator, Performing a transmission control unit reset, Running a diagnostic check to ensure normal transmission operation Total cost was 240€ and the slipping transmission issues completely disappeared after the repair. To better assist with your case, could you share: Does the issue occur more when the engine is cold or warm? Have you noticed any battery or electrical issues lately? Are there any other warning lights besides the transmission light? What is your current mileage? Since transmission problems can have various causes, these details would help determine if your issue is similar to what I experienced or if you might need a transmission flush or other repairs.

Thanks for your detailed response. I had my last service at 120461km about 2 weeks ago which included a routine oil replacement, but no transmission work was done. The issue mostly occurs when the engine is warm, usually after 15-20 minutes of driving. The transmission warning is the only light showing on the dashboard. No electrical problems noticed so far, the battery seems fine. After reading about your voltage regulator fix, I checked the battery voltage with a multimeter and it shows normal readings between 13.8-14.2V while running. Given these symptoms and the fact that no hydraulic fluid service has been done yet, I am leaning towards getting a transmission flush first. The automatic gearbox has never had its fluid changed since I got the car. Would you still suspect an electrical issue in my case, or does a transmission fluid problem sound more likely?

Thanks for those additional details, this actually sounds quite different from my voltage regulator issue, especially given your normal battery readings and the timing of when the problem occurs. The fact that the transmission problems show up when the engine is warm, combined with no previous transmission oil service, strongly points to degraded transmission fluid. Worn hydraulic fluid can break down under heat, leading to exactly the kind of erratic shifting behavior and emergency mode you are experiencing. After dealing with various transmission problems over the years, I would definitely recommend getting the transmission fluid checked and likely changed as a first step. When I finally had my transmission serviced at around 130000km, the old fluid was noticeably darker and had a burnt smell, clear signs it was overdue for replacement. Just ensure the workshop: Uses the correct specification transmission oil, Checks for metal particles in the old fluid, Replaces the transmission filter if recommended, Performs a proper transmission adaptation after the service A basic transmission oil service typically costs between 200-400€ depending on the amount of fluid needed. This is much more reasonable than diving into electrical diagnostics when the symptoms really point to fluid degradation. Would you mind updating the thread after you get it checked? It would help others with similar transmission performance issues know what to look for.

Given the symptoms and your explanation, I am convinced that a transmission fluid service is likely the solution. My initial concern about electrical issues seems less relevant now since the battery voltage is normal and the problem mainly occurs with a warm engine. The car has gone 120000km without any transmission oil changes, which alone is reason enough to start there. The automatic transmission showing problems after warming up is a classic sign of degraded hydraulic fluid that needs replacement. I will schedule an appointment with a workshop specializing in automatic transmissions next week. I will make sure they use the correct specification transmission oil and also have them check for any metal particles that could indicate bigger problems. Will definitely post an update once I get the results. Thanks for sharing your experience, it helped rule out the electrical system and focus on the more likely culprit of worn transmission fluid. The service cost estimate of 200-400€ seems reasonable compared to more extensive repairs.