Jetta Hybrid Stalling Issues: Start-Stop System Alert

This sounds very familiar to the issue I had with my 2017 Passat Hybrid last year. As someone with moderate experience maintaining hybrid vehicles, I can share my troubleshooting journey. The symptoms matched exactly, unexpected engine shutdowns and warning lights, particularly when the start-stop system was active. Initially, I thought it was just the eco mode acting up, but the problem got worse. After diagnostic testing, the workshop found that the car battery was severely discharged and not holding proper charge. This was affecting both the starter motor and the start-stop system functionality. The battery replacement and system reset cost me 290€, but it completely resolved the issues. What often happens with hybrid vehicles is that the constant cycling between electric and combustion power can put extra strain on the battery system. Before suggesting specific solutions, could you share: Current mileage on your Jetta, How long youve had these symptoms, Whether the issues occur more frequently in cold weather, If you use eco mode regularly, Any recent changes in driving patterns This information would help determine if youre facing the same battery-related problems I encountered.

At 82193km and just had service last month. The symptoms started appearing gradually over the past 3 weeks. The car battery was tested during service and showed normal readings, but the engine stalling happens more frequently now, especially during idle stop activation. The start-stop system warning appears consistently when the engine temperature reaches normal operating level. My daily commute hasnt changed, but the engine stalling occurs even without the idle stop feature enabled. The starter motor sounds normal during cold starts. The service records dont show any previous issues with the hybrid system components. Hoping someone here has experienced similar symptoms and can point me in the right direction before I take it back to the workshop.

Thanks for providing those details. Your situation sounds more complex than my initial battery-related issues. Since my Passat Hybrid repair, I learned that engine stalling in hybrid vehicles, particularly when not related to the start-stop system, often points to sensor malfunctions. When my car returned to the workshop, they discovered the engine control module was receiving incorrect signals from the crankshaft position sensor. This caused the engine stalling even with the idle stop feature disabled. The fact that your issues worsen at normal operating temperature matches this pattern. The repair involved: Replacing the crankshaft position sensor (320€), Reprogramming the engine control module, Calibrating the hybrid system sensors Since then, no more unexpected engine shutdowns or warning lights. Given your service history and mileage, I suggest having these components checked. The normal battery readings during your recent service support looking beyond the start-stop system for the root cause. The hybrid system requires precise sensor data to manage power transitions. When these sensors fail, it can trigger various symptoms that mimic start-stop system failures.

Thanks for sharing those details about the crankshaft position sensor. Your Passat experience definitely matches my symptoms, especially the part about stalling at normal operating temperature. The starter motor and car battery seem fine based on recent tests, but I need to investigate the sensor connections. Its helpful to know that hybrid vehicle stalling can be caused by sensor issues rather than just start-stop system problems. Im going to schedule a workshop visit and specifically request they check the crankshaft position sensor and engine control module. The fact that the engine stalling happens regardless of eco mode status makes me think youre right about the sensor diagnosis. Will update once I get the results from the diagnostic tests. My main concern was avoiding unnecessary parts replacement, but the sensor check seems like a logical next step based on your experience.