9-2-sistema-antiblokirovki-tormozov-abs-obshhaya-informaciya-i-kody-neispravnostejj.html

9.2. System of anti-blocking of brakes (ABS) - the general information and codes of malfunctions

The arrangement scheme on the car of the elements ABS

When the vehicle is equipped with brake system of usual type, sharp squeezing of a pedal of a foot brake leads to blocking of wheels. Coupling of a protector with a paving is thus broken, and the car can go yuzy, losing controllability. The system of anti-blocking of brakes (ABS) prevents premature blocking of wheels, continuously operating speed of their rotation during braking at the expense of modulations of pressure of hydraulic liquid in each of brake mechanisms.

ABS consists of two main subsystems: electric and hydraulic. Four sensors of speed of rotation of wheels, the sensor enter into an electric part of system accelerations (G-sensor), the electronic control unit (ECU) and a set of connecting electroconducting (see an illustration the arrangement Scheme on the car of the elements ABS). The hydraulic part includes the pressure modulator, supports / wheel cylinders of brake mechanisms and connecting components lines of communication.

The principle of functioning of system is rather simple. Each of wheels is equipped with the individual sensor of turns. The sensor consists of a rotor (a ring with teeth evenly located on its perimeter) and a sensitive element in the form of the podmagnichenny coil. The sensitive element of the sensor fixes the moments of passing of teeths of a rotor by it and will transform received information to the electric signals which are continuously transferred to the ABS control unit. By results of processing of arriving signals of ECU receives information on relative speed of rotation of each of wheels. While all four wheels rotate with identical frequency, ABS stays in a passive condition. As soon as any of wheels starts to be blocked, the control unit fixes change of an entering signal and develops command for operation of the modulator which is instantly dumping pressure of hydraulic liquid in the brake mechanism of the corresponding wheel. As soon as normal rotation of a wheel is restored, the processor stops modulator functioning. Let's notice that switchings of the modulator can occur to speed of one hundred times a second.

One more element ABS used on the Infiniti QX4 models, the sensor accelerations (G-sensor) is. Normally closed yazychkovy G-sensor is established under assembly of the central console in car salon (ahead of the lever of the parking brake) and serves for transfer on the module of management of ABS information on the overloads arising during dispersal or braking of a vehicle. The analysis of arriving signals together with the data accepted from wheel sensors, and information on working parameters of the power unit allows the processor of the module to define reliability of coupling of protectors of wheels with a paving and to exercise administration of functioning of the hydraulic modulator taking into account this factor.

Actually the scheme of functioning of ABS is much more difficult, than it can seem, therefore originators of the real Management do not recommend to owners of cars to make attempt of independent performance of repair of system. In case of malfunctions it will be most reasonable to address to specialists of car-care center.

At identification of any sort of violations of functioning the ABS control unit carries out transition of system to emergency operation by disconnection of a food from the hydromodulator, thus the corresponding diagnostic code is brought in memory of system of self-diagnostics, and the brake system continues to work in a usual mode (without ABS).

ABS problem diagnostics

Preliminary checks

Check level of brake liquid. If level in norm, pass to the following stage of check, otherwise check a condition of brake shoes and investigate a hydraulic path of system on existence of signs of development of leaks. Eliminate debugged, in case of need make replacement of blocks, or correct level by addition in the GTTs tank of the corresponding amount of hydraulic liquid of a demanded grade.

Estimate serviceability of functioning of standard brake system (including checks of a condition of the vacuum amplifier and correctness of adjustments of brake mechanisms and the parking brake). Make necessary corrections.

Include ignition, and make sure of serviceability of operation of a control lamp of ABS (see. Head Maintenance instruction). Start the engine — the control lamp of ABS should go out. At refusals of a control lamp it is necessary to make reading brought in memory of the processor of codes of malfunctions (see below) — told over 30 km/h and movements in this mode within not less than 1 minute belong as well to cases of operation of a control lamp after car dispersal till the speed.

Reading of codes of malfunctions (DTC) of ABS

Reading of the DTC codes by means of a control lamp of ABS

At identification by the processor of malfunctions in system in an instrument guard lights up and remains to ABS included a control lamp. Diagnostics of malfunctions of anti-blocking system is among enough difficult procedures and originators of the real Management do not recommend to make it in house conditions. Nevertheless, it is possible to allocate a number of the elementary checks which can be quite successfully made by own strengths of the owner of the car and allow to define qualitatively a cause of failure (see further).

Codes can alternatively be считаны by means of a control lamp of ABS: by means of a wire crossing point earth the CONSALT socket plug No. 4. Without squeezing out a pedal of a foot brake, include ignition. About 3 seconds later the control lamp will start to give out flashing signals, highlighting brought in memory of the processor codes. The figure of tens of code is defined by quantity of gleams of a lamp, duration for 0.6 seconds divided among themselves by pauses of the same duration, the figure of units of a code is separated by a pause duration of 0.9 seconds. The figure of units of a code is defined by quantity of gleams of a lamp, duration for 0.3 seconds. The moment of the beginning of reading is noted by code 12 delivery (one gleam, a pause, two gleams). Then again follows long (3.3 seconds) a pause after which the lamp starts to highlight being stored in memory of the control unit codes.

At first the lamp always highlights a code of the beginning of reading (12), further there are DTC codes (to three in a row, since the last) (see an illustration Reading of the DTC codes by means of a control lamp of ABS). Completion of process proves to be true in repeated highlighting of a code 12. If the code 12 is highlighted only, and the symptom of refusal takes place, the car should be driven away on car repair shop for performance of standard diagnostic checks according to the card of symptoms. In memory of the processor the simplest malfunction can be the reason of introduction of a code — first of all make the following checks:

• Make sure of correctness of level of hydraulic liquid in the GTTs tank;
• Check a condition of contact connections of the corresponding electric chains;
• Check a condition of safety locks;
• Check a condition of brake system;
• Check a condition of brake shoes;
• Check a condition of a pedal of a foot brake.

The following belongs to number of diagnostic checks of symptoms entering into the card:

The ID card of codes of malfunctions of ABS is given in Specifications.

Cleaning of memory of the ABS processor

After elimination of the revealed malfunctions in system memory of the processor should be cleared. Cleaning of memory can be made either by means of the scanner, or by double grounding of the plug No. 4 for 1 second during a 12.5-second interval — during the whole time of removal of codes the control lamp of ABS remains included, then should go out.

More detailed information on the skanerny input reader is provided in Head of the Power supply system and management.