Abstract
For OBD-equipped vehicles, ISO and SAE regulations specify standards both for on-board communication protocols as well as communication with external diagnostic readers. One of the reasons behind the introduction of the
OBD system was to enable independent hardware manufacturers, not aligned to well-known automotive corporations, to produce their own diagnostic devices. As a result, the automotive service shop equipment market has seen and is still to see a whole range of devices differing in their functionality, technical specifications, design, and in their manufacturers' research and development resources. The main problem encountered during their design and production phases is to ensure their full compliance with the OBD standards.
The range of instrument testing on actual vehicles is limited. For example, controlled enforcement of all values for all the return current parameters, or generating all the trouble codes is unfeasible. The problem of how to validate the soundness of design and implemented communication algorithms can only be solved by developing a software and hardware implementation that could be used to perform all-round examination of all the layers of OSI model of any diagnostic reader. To serve its purpose, such a system would have to feature a function to carry out examination of consistency with respect to electrical signal levels, their transition times, and the logical layer of communication protocols. Since the general OBD (OBDII/EOBD) standard already encompasses a number of different communication protocols (J1850 PWM, J1850 VPW, ISO-9141, ISO14230 - KW2000, CAN), effectuating a project that would validate readers for their consistency, or compliance with obligatory regulations would entail a great measure of sophistication and a high degree of technological advancement.
The paper examines the structure of so developed a system, its functions, and ways of implementing them. It also includes a brief presentation of Microsoft Windows compatible software designed to control the diagnostic process and provide its graphic representation. Furthermore, additional software is presented whose function is to exami-ne specific features of OBD-interfaced devices developed for the German market (assessment of switching and wide-range oxygen sensor condition based on the registration and analysis of time series of instantaneous voltages). The technical discussion is substantiated with sample examination results obtained by testing a number of devices available on the market (whereby the manufacturer identity is not disclosed, however). The examples conclude with assessment of detected deviations from obligatory regulations.