On-board diagnostic and vehicle electronic controls

OData support
Hajdu István
Department of Electronics Technology

I begin my summary with the theoretical part. To write my essay, i have studied the development of vehicles’ diagnostic systems, since the beginning to nowadays. I have explored the OBD-I, OBD-II, CAN-Bus systems and standards. I have studied their structure, their function and working method. I paid high attention to error codes and emission surveillance. I specified the data protocols, the structure of messages and the importance of the structure for the CAN-Bus networks. I listed some of the possible gauges for diagnostics in different price categories.

The main equipment responsible for the supply of power for the vehicle is the generator, which can also be analysed with the help of diagnostic tools. The generator keeps the voltage and current level of the accumulator in a given threshold. This unit can be put on a test bench after removing it from the vehicle, and its proper operation can be verified with diagnostic tools. I thoughtfully examined the structure, working method, and the different regulating methods of dynamos (used in vehicles before the invention of generators), and alternators. I portrayed the different variations of voltage regulation, because this is the unit that is responsible for the correct operation of the generator and the accumulator.

I have performed a high number of different measurements to compare the different vehicle diagnostic instruments from a practical standpoint. I have studied the more versatile, more expensive instruments (Bosch, Guttmann, Delphi), and two simpler, cheaper models. I noted down the utilization possibilities based on measurements on multiple vehicles. I tested the diagnostic instruments on real errors too. With their help and manual intervention, the errors were successfully corrected, and they were removed from the central processing unit.

I have conducted my work about generators in the vehicle laboratory of BME, with the operational generator test pad. I performed the measurements that the state of the pad made possible. I analysed the systems faults, and i made a suggestion to improve the pad with the addition of a frequency modifier. I set up a Lenze frequency modifier temporarily, so i could demonstrate the possibilities with the upgrade. The pad was then capable of simulating the generators power output voltage regulation and behaviour under different loads more realistically, because i could set up a more realistic rev.

After my measurements i procured quotations, and i made a suggestion to purchase one of the frequency modifiers on the market (there is an example in my work).

The prepared practical and theoretical documentations provide a good foundation for students, for the measurement exercises of the BME Vehicle laboratory, in the fields of diagnostics and the study of generators. (My work doesn’t contain every measurement because of their size.)


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