Diesel Exhaust Fluid / Water In Fuel Light | How To | 2025 Ram Heavy Duty Trucks

Your Ram Heavy Duty Truck's diesel engine uses diesel exhaust fluid (DEF) to help clean diesel exhaust emissions.
There are times when water may accumulate in your Ram Heavy Duty Truck's diesel fuel system. Unlike a gas fuel system, water in diesel fuel may cause damage to diesel engine parts. Because of this, diesels generally have a warning message that will illuminate.