Will a key fob from a Passat start a Jetta

Hi, my name is Devin. I am an auto repair expert with the Car Genius team here at RepairPal. A key fob from a Passat will not start a Jetta. Each Volkswagen key fob is specifically programmed to the vehicle's immobilizer system, which is unique to that car. Even if the fobs look similar, they won't work across different vehicles due to the programming differences. If the Jetta isn't starting now, it could be a separate issue with the key fob battery or the car's immobilizer system. If you need more advice, have any other questions about your vehicle, or would like to get connected to a RepairPal Certified shop near you, we have you covered. Give us a call at 877-913-1554, and we will happily help you out!