All models described in this Manual are equipped with a second-generation on-board diagnostics system (OBD II). The main element of the system is the on-board processor, more often called the electronic control unit (ECM) or the powertrain control unit (PCM). The PCM is the brain of the engine management system. Initial data is sent to the unit from various information sensors and other electronic components (switches, relays, etc.). Based on the analysis of data received from the information sensors, and in accordance with the basic parameters stored in the processor memory, the PCM generates commands to operate various control relays and actuators, thereby adjusting the engine operating parameters and ensuring maximum efficiency with minimum fuel consumption. Reading of the OBD-II processor memory data is performed using a special scanner connected to a 16- or 38-pin diagnostic connector for reading the database (DLC), located in the car's interior.
Note: In principle, reading the fault codes recorded in the memory of the self-diagnostic system is possible, on some models, using an auxiliary LED, as well as using the codes displayed on the automatic KV display.
Information about diagnostic devices
The proper functioning of the injection system components and the reduction of exhaust gas toxicity is checked using a universal digital meter (multimeter). Using a digital meter is preferable for several reasons. Firstly, it is quite difficult to measure the value of an analog meter (sometimes it's impossible), determine the result of the reading with an accuracy of up to hundredths and thousandths, while when examining circuits that include electronic components, such accuracy is of particular importance. The second, no less important, reason is the fact that the internal circuit of the digital multimeter has a fairly high impedance (the internal resistance of the device is 10 MOhm). Since the voltmeter is connected to the circuit being tested in parallel, the accuracy of the measurement is higher, the smaller the current that passes through the device itself. This factor is not significant when measuring relatively high voltage values (9 - 12 V), but it becomes decisive when diagnosing elements that produce low-voltage signals, such as, for example, a lambda probe, where we are talking about measuring fractions of a volt.
Parallel monitoring of signal parameters, resistances and voltages in all control circuits is possible using a splitter connected in series to the engine control unit connector. In this case, with the engine off, running or while the car is moving, the signal parameters are measured at the splitter terminals, from which a conclusion is made about possible defects.
For diagnostics of electronic systems of the engine, automatic transmission, ABS, SRS and others, special diagnostic scanners or testers with a specific cartridge can be used (if provided), a universal cable and connector. In addition, for this purpose, you can use an expensive specialized automotive diagnostic computer, specially designed for full diagnostics of most systems of modern cars (for example, ADC2000 from Launch HiTech). Also, for this purpose, you can use scanners and specialized diagnostic analyzers, for example FDS 2000, Bosch FSA 560, KTS 500 (0 684 400 500) or a regular personal computer with a special controller, cable (for example, set 1 687 001 439) and the installed OBD II browser program.
Some scanners, in addition to the usual diagnostic operations, allow, when connected to a personal computer, to print out the basic diagrams of electrical equipment stored in the control unit memory (if pledged), program the anti-theft system, observe signals in the car circuits in real time.