Toyota Land Cruiser 100/Amazon, Lexus LX 470

since 1997 release

Repair and operation of the car

System of onboard diagnostics (OBD) – the principle of functioning and codes of malfunctions

Data on diagnostic units

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 (internal resistance of the device makes 10 million Ohms). As the voltmeter is connected to the checked chain in parallel, the accuracy of measurement of subjects is higher, than smaller parasitic current will pass through actually device. This factor is not essential at measurement of rather high values of tension (9 – 12 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.

With introduction to production to meeting requirements of the last legislations for environmental protection of system of onboard diagnostics of the second generation (OBD-II) readers of a special design began to be issued. Some producers marketed the scanners intended for use by amateur mechanics in house conditions, – ask in shops of automobile accessories.

General information

The scheme of an arrangement of components of control systems of the engine and decrease in toxicity of the fulfilled gases on models with the V8 engine

Electronic systems of injection and decrease in toxicity of the fulfilled gases in the course of the functioning at operation of the car are crossed with various other systems which are responsible for efficiency of return of the engine. All listed systems turn on a set of information sensors and the electronic module of management (ESM) in the structure (address an illustration above).

Systems of this sort can be compared on the structure to the central nervous system of a human body where a role of a brain is played by the module of management (ESM), and information sensors act as the nervous terminations. Sensors send signals to ESM which analyzes the arriving information and develops response commands for adjustment of the corresponding working parameters.

Let's review the specific example allowing to imagine more clearly the principle of functioning of system: built in in system of release a lambda probe continuously traces the level of contents _{O 2} in a stream of the fulfilled engine gases. If percentage of oxygen considerably deviates some control value entered into memory of system, ESM immediately obtains the relevant information and on the basis of its analysis develops the command for the corresponding adjustment of duration of opening of injectors of fuel, carrying out thereby adjustment of composition of air-fuel mix. Duration of the described procedural cycle makes fractions of a second that provides due efficiency of functioning of system. As a result, efficiency of return of the engine is constantly maintained at the greatest possible level.

Reading of codes of malfunctions of OBD-II

In the OBD-II system five-digit codes of the revealed malfunctions are brought in the processor memory (ESM).

It is necessary to notice that the system of onboard self-diagnostics is capable to find not all possible refusals, – in case of need do not hesitate to address for consultations on company car repair shops of the Toyota company. During search of the reasons of decrease in efficiency of return of the engine, increase in fuel consumption or level of toxicity of the fulfilled gases (these violations usually are not followed by operation of a control lamp "Check the engine") it is necessary to make first of all all complex of standard checks regarding identification of the reasons listed in the Section devoted to diagnostics of malfunctions of systems and knots of the car in introduction to the present manual and only after it to switch to the OBD system.

It is necessary to remember that use of OBD-II demands from the operator of basic knowledge in the field of automobile electronics, non-compliance with precautionary measures at the address ESM and other electronic components can lead to an irreversible exit of system out of operation.

The list of the diagnostic OBD-II codes of the most typical system failures is presented in the table given below. If it is not possible to reveal and remove a cause of failure independently, the car should be driven away on car repair shop for the purpose of performing diagnostics with use of the special diagnostic equipment.

Cleaning of memory of OBD-II

For cleaning of memory of ESM connect the scanner to system and in an apportion of its menu choose the CLEARING CODES function ("Removal of codes"). Further follow the instructions highlighted on the device or at once for 30 seconds take from the nest in the assembly block EFI safety lock. Alternatively cleaning of memory of system can be made by removal of a fusible insert (the main safety lock of the system of onboard power supply) installed close the positive plug of the battery (see. Onboard electric equipment) (it is possible also just to disconnect a positive wire from the battery).