Mercedes M-Class W163

since 1997 of release

Repair and car operation

Diagnostics of systems of electronic control and diagnostic equipment

The structure of OBD system includes some diagnostic devices making monitoring of separate parameters of systems of decrease in toxicity and fixing revealed refusals in memory of the onboard processor in the form of individual codes of malfunctions. The system makes also check of sensors and actuation mechanisms, supervises vehicle service cycles, provides storing possibility even failures quickly arising in the course of work and cleaning of the block of memory.

All models described in the real Management are equipped with system of onboard diagnostics of the second generation (OBD II), which basic element is the onboard processor more often called by the electronic module of management (ECM - further), or more rare) the module of management of functioning of the power unit (RSM).

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 data arriving from information sensors, and according to put in memory of the processor in base parameters, 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.

Data read-out of memory of the OBD II processor (ECM) is made by means of the special scanner connected to the 16-contact diagnostic socket of reading of a database (DLC). By means of the same scanner cleaning of memory of the processor is carried out also. And cleaning of memory of ECM it will be reasonable to charge performance of procedures of reading of the DTC codes to specialists of car-care center.

On some models reading of the ECM codes of malfunctions (DTC) written down in memory in principle can be made by means of an auxiliary light-emitting diode, and also on the codes highlighted on the display automatic К/В.

The DLC socket is located at the left under the car dashboard

Identification of plugs of the 16-contact diagnostic socket (DLC)

Data on diagnostic devices

Check of serviceability of functioning of components of systems of injection and decrease in toxicity of the fulfilled gases is made by means of a universal digital measuring instrument (multimeter). Use of a digital measuring instrument preferably 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 in the structure electronic components, such accuracy takes on special significance. The second, the reason that fact is not less important that the internal contour of a digital multimeter, has rather high impedance (internal resistance of the device makes 10 megohms). As the voltmeter is connected to a checked chain in parallel, accuracy of measurement by that is higher, than the smaller current will pass through actually device. This factor is not essential at measurement of rather high values of tension (9 ÷ 12 In), however there is defining at diagnostics of elements giving out low-voltage signals, such, as, for example, a lambda probe where it is a question of measurement of shares of volt.

Multimeter connection to control unit sockets the engine by means of an auxiliary splitter

Parallel supervision of parameters of signals, resistance and tension in all chains of management is possible by means of a splitter included consistently in the socket of the control unit by the engine. Thus on the switched-off, working engine or during car movement, measurement of parameters of signals on splitter plugs from what the conclusion about possible defects is drawn is made.

Special diagnostic scanners or testers can be applied to diagnostics of electronic systems of the engine, automatic transmission, ABS, SRS and other with a certain cartridge (if it is provided), a universal cable and the socket. Besides, it is possible to apply the expensive specialized automobile diagnostic computer which has been specially developed for complete diagnostics of the majority of systems of modern cars to this purpose (for example, Launch HiTech firm ADC2000). Also, it is possible to apply 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 established program OBD II browser.

For diagnostics of your car you can download the free version of a browser of OBD II also from a site of originators of the real Management.

Some scanners, besides usual operations of diagnostics, allow, at connection with the personal computer, to unpack being stored in memory of the control unit schematic diagrams of electric equipment (if those are put), to program anticreeping system, to observe signals in car chains in real time.