Engine Management System Diagnostics (BMW 7 Series E38)

On-Board Diagnostics (OBD) System

The models are equipped with a second-generation on-board diagnostics system (OBD II).

Reading of OBD II system data is performed using a special scanner, for example, Consult-II, connected to a 16-pin diagnostic connector (DLC) via a special cable with an adapter. The same scanner is used to clear the processor memory. It would be reasonable to entrust the procedures for reading DTC codes and clearing the ECM memory to service station specialists.

Information about diagnostic devices

The proper functioning of the injection system components and the reduction of exhaust 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 - impossible), determine the result of the reading with an accuracy of 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. Since the voltmeter is connected to the circuit being tested in parallel, the accuracy of the measurement is higher, the lower 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 splitter, connected in series to the engine control unit connector. In this case, with the engine turned off or running, or while the car is moving, the parameters of the signals at the terminals of the splitter are measured, from which a conclusion is made about possible defects.

To diagnose the electronic systems of a car, special diagnostic scanners or testers with a specific cartridge can be used (if provided), universal cable and connector. In addition, for this purpose, you can use a specialized automotive diagnostic computer, specially designed for full diagnostics of most systems of modern cars (for example, ADC2000 by Launch HiTech). Also, for this purpose, you can use scanners and specialized diagnostic analyzers, for example, FDS 2000, Bosch FSA 560 (bosch.de), KTS500 (0 684 400 500) or a regular personal computer with a special adapter, 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 memory of the control unit (if any are included), program the anti-theft system, monitor signals in the car circuits in real time.