The purpose of the study is to carry out the experimental tests for the propulsion unit of the selected passenger car i.e. Skoda Felicia 1.3 MPI provided with Simos 2P system (manufactured by Siemens). The tests were carried out by means of an appropriate measuring equipment, among others AOC1K oscilloscope (digital recorder integrated with PC by means of RS232 interface) and a personal computer. The measurements of signals on the contacts of the electronic control device encompass the measuring procedures for individual signals, in accordance with the contact symbols: the camshaft position sensor, the engine speed sensor, the lambda probe, the pressure sensor, the throttle position sensor, the idle speed control actuator, the knock sensor. In some cases it is impossible to confirm the standard codes by the execution of diagnostic tests of the modern control system of ZI combustion engine, using the Simos 2P system.