The 03-04 5.9L Common Rail Cummins debuted in 2003 and continued through mid-2004. To easily identify the 03-04 motor there is a white label on the driver side of the valve cover that has engine specs, there is a line that states engine horsepower and it will read 305hp (if it reads 325hp, it is a 04.5-07 H.O. Cummins motor). This 03-04 Common Rail Cummins was the first of its kind, upgrading to a bigger turbo, high-pressure common rail injection system, CP3 injection pump that pushes up to 24,000psi, and feeds into a new style Bosch injector. The whole motor and control system is ran off a CAN bus system which means everything communicates with each other through micro controllers. The CP3 injection pump runs off a gear within the timing cover but it is completely regulated by electronics which feeds a Bosch injector that is individually regulated by solenoids. This all seems pretty complex but it opened the doors for refined tuning. One of the main issues with the 03-04 Cummins trucks is a result of improper fuel filtration and lift pump failure which can be fixed by adding a Fass or an AirDog lift pump. Like in earlier years, the 03-04 Dodge truck still had front suspension/steering issues with the Y-style steering linkage which can create death wobble under load or acceleration. The 03-04 Cummins is equipped with a 48re transmission which are great transmissions, they are just built weak from the factory. An upgraded transmission rebuild kit or crate transmission and torque converter will make these transmissions near bulletproof. Also, the 03-04 Dodge truck could have been equipped with a NV5600 manual transmission.