Abstract: A method for cooling an ECU and an ECU or ECU module mounted to be cooled by fuel flow through a fuel rail. In a preferred embodiment, the ECU has a decentralized distributed processing configuration, with a main ECU module and at least one remote module. The remote ECU module is packaged in an assembly with an elongate hollow metal fuel rail having injector seats. Fuel injectors are received into and seal against the seats and are supplied with fuel via the fuel rail. A printed circuit board carries electronic ECU components. One or more connector assemblies are connected to printed circuit board for electrically connecting the ECU circuitry and may pass through notches formed in the fuel rail. The electronics are potted and mounted to the fuel rail. A thermally conductive wetting compound may be disposed between the electronic assembly and the fuel rail.