Abstract: A method for calibrating an electronic control unit for an internal combustion engine. The electronic control unit may have multiple channels with each channel being adapted to provide an input drive signal to a fuel delivery apparatus. A first channel is selected for calibration. A reference signal of desired and known parameters is also defined. The reference signal is defined such that it is indicative of the cyclical performance of a fuel delivery apparatus such as a fuel injection device. A command signal is generated and passed through the circuitry of the selected channel. The channel circuitry generates a drive signal in response to the command signal. A desired parameter of the drive signal is measured for comparison with the known parameter of the reference signal. If necessary, the command signal is then adjusted so as to produce a modified drive signal which has a parameter with reduced variation from the known reference parameter.