Changing some of the parameters of the engine structure affects the emission of harmful components in the exhaust gases This primarily concerns damage in the cargo exchange system as well as in the fuel system and engine boost system. Changes in emissions of harmful compounds are often ambiguous, depending largely on the parameters that shape the combustion process. An additional problem is that often simple but undesired interactions occur with the interaction of these parameters. It is therefore possible to speak of different diagnostic parameters sensitivity to the same extractions from the engine structure, but implemented in other load states. In cases where the set of parameters is numerous and the values of these parameters are similar, there is a real problem with their proper classification, often based on the discretion of the researcher. In the paper the authors propose a methodology for classification of acquired diagnostic parameters. In previous papers [4, 5], Hellwigs method of information capacity index was proposed as a measure of diagnostic parameter sensitivity. This method can be used to build a diagnostic parameter ranking that divides the set of diagnostic variables into stimulators, destimulators and nominators. This normalization of the set seems to be helpful in making a diagnostic decision not influenced by the discretion of the researcher. The zero unitary method can also be helpful in creating diagnostic tests.