My 2015 Ford Fusion with the 1.5L EcoBoost engine experienced a complete engine failure due to a coolant intrusion in cylinder 3, which is consistent with Ford TSB 20-2100. In December 2023, I brought the car to the dealership due to rough starting and a non-start issue. No coolant related codes were detected at the time. In May 2025, the vehicle began running roughly and showed codes PO316 and PO303. The dealership diagnosed low coolant and coolant intrusion into cylinder 3, with a rust and fouled spark plug. I believe this is a progressively safety-related engine defect that can lead to sudden loss of power and unsafe driving conditions.