The Bosch EDCxx series (Electronic Diesel Control) ECUs is a widely used system for modern diesel engines. It is used by BMW, VAG, Opel, SAAB and many others. This document and the described VAG EDC15P suite software will only focus on the Volkwagen Audi Gruppe (VAG) specific implementations in the EDC15P models. These ECUs are used in the PD engines (Pumpe Duse) from Volkswagen, Audi, Skoda and Seat. Other EDCxx ECUs may work in a similar fashion but will differ in certain areas. The document describes the EDC15P ECU in detail. It will first describe the hardware and proceed with a even more detailed description of the software that is running in the ECU so that we can learn how to tweak and tune the ECU to match the hardware – altered or not – that is on the car better.