7.2.1. General information
System of onboard self-diagnostics (OBD)
Several diagnostic devices making monitoring of separate parameters of systems of the car and fixing the revealed refusals in memory of the onboard processor in the form of individual codes of malfunctions are a part of the OBD system.
The models described in the present manual are equipped with system of onboard diagnostics of the second generation (OBD II) which basic element is the onboard processor more often called by an electronic control unit (ECM).
ECM is a brain of a control system of the engine. Basic data arrive on the module from various information sensors and other electronic components (switches, the relay, etc.). On the basis of the analysis of these data, and according to the basic parameters put in the processor memory, ECM develops commands for operation of various operating relays and actuation mechanisms, carrying out thereby adjustment of working parameters of the engine and providing maximum efficiency of its return at the minimum fuel consumption.
Communication between ECM and DLC No. 3 is organized in ISO 9141-2. Contacts in DLC No. 3 are located according to the SAE J1962 and ISO 9141-2 standards.
Contacts of the DLC socket No. 3
||4 — Connection with the case
5 — the Case - an alarm conclusion
7 — the Line K of diagnostic data (ISO 9141-2)
15 — the Line L of diagnostic data (ISO 9141-2)
16 — battery Tension through a safety lock (at any position of the lock of ignition)
Data on diagnostic units
Check of serviceability of functioning of components of systems of injection and decrease in toxicity of OG is made by means of the universal digital measuring instrument (multimeter). Use of the digital measuring instrument is preferable for several reasons. First, on analog devices it is rather difficult (sometimes - it is impossible), to define result of the indication to within the 100-th and thousand shares while at inspection of the contours including electronic components in the structure, such accuracy is of particular importance. The second, not less important, the fact that the internal contour of a digital multimeter, has rather high impedance is the reason. As the voltmeter is connected to the checked chain in parallel, the accuracy of measurement of subjects is higher, than smaller current will pass through actually device. This factor is not essential at measurement of rather high values of tension (9÷12 of V), however becomes defining at diagnostics of the elements giving low-voltage signals, such as, for example, lambda probe where it is about measurement of shares of volt.
Parallel observation of parameters of signals, resistance and tension in all chains of management is possible by means of the splitter included consistently in the socket of the control unit of the engine. At the same time on the switched-off, working engine or during the movement of the car, measurement of parameters of signals on splitter plugs is performed from what the conclusion about possible defects is drawn.
Special diagnostic scanners or testers with a certain cartridge (if it is provided), a universal cable and the socket can be used to diagnostics of electronic systems of the engine, AT, the ABS, SRS systems and other. Besides, it is possible to use the expensive specialized automobile diagnostic computer which is specially developed for full diagnostics of the majority of systems of modern cars to this purpose (for example, ADC2000 of Launch HiTech). Also, it is possible to use scanners and specialized diagnostic analyzers to this purpose, for example, FDS 2000, Bosch FSA 560, KTS500 (0 684 400 500) or the ordinary personal computer with the special adapter, a cable (for example, a set 1 687 001 439) and the installed program OBD II browser.
The free version of a browser of OBD II it is possible also<скачать> from the website of authors of the present manual arus.spb.ru.
Some scanners, besides usual operations of diagnostics, allow to print out, at connection with the personal computer, the schematic diagrams of electric equipment which are stored in memory of the control unit (if those are put), to program anticreeping system, to observe signals in car chains in real time.