VW Golf Hybrid Transmission Failure Linked to Oil Pressure

Had almost the exact same issue with my 2016 VW Passat GTE Hybrid at around 90000km. Having some experience with hybrid drivetrains, I knew these symptoms could be related to the cooling system affecting transmission performance. The radiator coolant pressure was fluctuating due to a faulty sensor connection near the oil cooler assembly. The transmission was going into safety mode because it wasnt getting accurate pressure readings from the cooling system. The check engine light came on for the same reason. Took it to a specialized workshop where they diagnosed a loose connector that was causing intermittent signal issues between the pressure sensor and the transmission control unit. The repair involved replacing the wiring harness connector and recalibrating the sensor. Total cost was 95€ and took about 2 hours to complete. Since the fix, the transmission has been shifting smoothly with no warning lights. The car overheating concerns also disappeared once the cooling system was reading correct pressure values. Could you share: Any diagnostic trouble codes from the scan? Does the issue happen more during cold starts or after the engine is warm? Have you noticed any radiator coolant level changes? When was the last cooling system service done? This information would help determine if your case is similar to what I experienced.

Had the same symptoms with my Golf hybrid at 86352km. Just had it serviced last month and discovered the coolant leak was causing transmission problems. The cooling fan wasnt activating properly, which led to irregular oil cooler temperatures affecting the transmission. The repair involved: Pressure testing the entire cooling system, Replacing faulty coolant temperature sensors, Installing new radiator seals, Updating transmission control software Total repair cost was 780€ and the car was in the shop for 3 days. Since the fix, transmission shifts perfectly and no more warning lights. Make sure they check the cooling system thoroughly as it impacts hybrid transmission performance more than conventional cars. The car overheating symptoms completely disappeared after the radiator repair. Worth checking if your coolant levels are correct, as low coolant can trigger similar transmission warnings. Would your mechanic be willing to do a complete cooling system pressure test before diving into transmission repairs?

Thanks for sharing those repair details, very helpful information about the cooling system connection to transmission problems. My Passat had slightly different symptoms but a similar root cause. The oil cooler malfunction actually turned out to be more complex than initially diagnosed. After the first repair attempt with just the connector replacement, the transmission started acting up again after about 2 weeks. Further testing revealed micro-cracks in the oil cooler housing causing pressure loss. The complete fix required: Full cooling system pressure test, Replacement of the oil cooler assembly, New coolant temperature sensors, Transmission fluid flush Final repair cost was 850€ and took 4 days total. The coolant leak was very small and hard to spot initially, but the pressure test confirmed the issue. The transmission problems completely resolved once proper cooling system pressure was restored. Your mechanic took the right approach with the comprehensive testing. These hybrid transmissions are very sensitive to cooling issues, even minor coolant leaks can trigger multiple warning lights and protective modes. Have you noticed any fluid spots under the car since the repair? Might be worth doing another pressure check in a few months as preventive maintenance.

Thanks for that additional insight about the micro-cracks, makes total sense now. No fluid spots since the repair, but I will definitely schedule another pressure test in 3 months as suggested. After my experience, I learned these hybrid transmissions really depend on precise cooling system operation. The radiator repair solved multiple issues I didnt even know were connected. My mechanic found small traces of coolant near a hose connection that were almost impossible to spot without the pressure gauge test. For anyone else reading this with similar symptoms, get your cooling system checked first. A proper pressure test saved me from unnecessary transmission work that could have cost thousands. The service manual actually states that transmission fault codes can trigger from cooling system problems, but many shops miss this connection. The total repair cost of 780€ was much better than the 3000€+ initially quoted for transmission work. Monthly checks of coolant levels and watching for any car overheating signs are now part of my maintenance routine.