The invention relates to a method and a device for identifying errors in emission-relevant control devices of a vehicle, such as the injection of fuel into a cylinder. The aim of the invention is to provide a method and a device that allow error identification even if none of the sub-systems exceeds a predetermined threshold value. The aim is achieved by a claimed method and device for identifying errors in a plurality of emission-relevant control devices. The method has the following steps: determining whether at least one parameter, which permits conclusions to be drawn about the emission behaviour of the respective control device, lies in a desired range; if the parameter lies outside said desired range, an error value that correlates to an increase in emissions is stored; if the parameter is in the desired range, an error value of zero is stored; a total error value is formed from all error values of the control device and an error message is output if the total error value exceeds a predetermined threshold value.