Due to tolerances when manufacturing the injectors the injected fuel quantity may deviate between the actual and calculated fuel quantity. After manufacture these deviations are determined for every injector and a calibration value is determined, the value is converted to a code that is stamped on the injectors. This code is programmed in the engine control unit for each cylinder. Using these codes, the engine control unit corrects the calculated fuel quantity individually for each cylinder and thus improves engine operation and exhaust emissions. With this function, new calibration values can be entered in the engine control unit when replacing injectors or the engine control unit.