Toyota Land Cruiser 100/Amazon, Lexus LX 470

since 1997 release

Repair and operation of the car

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

General information

Typical scheme of an arrangement of the ABS components

Electronic control unit (ECU) of ABS

ECU of the ABS system is fixed under a forward overlay of a threshold of the right door.

ECU traces the speed of rotation of each of car wheels, being guided by the arriving signals from wheel sensors. When at emergency braking any of wheels it begins to be blocked prematurely, ECU issues the command for activation of the hydraulic modulator of the electromagnetic valve placed inside which, working, opens the respective site of a brake contour, releasing from it a part of working liquid in the tank and, respectively, reducing working pressure. As soon as speeds of rotation of wheels are equalized, the valve is closed again and pressure continues to rise. The cycle lasts fractions of a second on each of wheels and repeats until braking is not complete. The design of system allows to correct pressure in hydraulic contours of each of four wheels. Actually the scheme of functioning of ABS is much more difficult, than it can seem therefore authors of the present manual do not recommend to owners of cars to make attempts of independent performance of repair of system. In case of malfunctions it will be most reasonable to address specialists of car service.

Hydraulic modulator

The modulator is installed in a motive compartment and equipped with the electromagnetic valve of adjustment of hydraulic pressure working at the command of ECU in contours of the brake system.

Wheel sensors

Each of wheels is equipped with the individual RPM meter. The sensor consists of a rotor (a ring with the teeth which are 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 rotor teeths by it and will transform the obtained information to electric signals, control of ABS which are continuously transferred on the module. By results of processing of the arriving signals of ECU obtains information on the relative speed of rotation of each of wheels. While all four wheels rotate with an identical frequency, ABS stays in a passive state. As soon as any of wheels begins to be blocked, the control unit fixes change of the entering signal and develops the command for operation of the modulator which is instantly dumping pressure of hydraulic liquid in the brake mechanism of the corresponding wheel.

Sensor switch of stoplights

Determines the moment when the driver squeezes out a pedal of a foot brake by the signals arriving from the sensor switch of stoplights of ECU, at once activating ABS.

Diagnostics and recovery repair

If the control lamp of ABS which is built in in the car dashboard lights up and continues to burn during the movement, first of all make sure that the parking brake is completely released, and the brake system functions regularly. If all normal, therefore, there was ABS refusal. At the same time in memory of ECU the malfunction code has to be brought. At diagnostics and reading of codes of malfunctions the warning bulb on the dashboard will blink. In the presence of several codes, their indication will be begun with smaller number on increasing, regardless of time of their receipt. At the movement of the car codes of malfunction are not displayed. Perform visual inspection:

1. Check a condition of brake supports and wheel cylinders;
2. Check a state and reliability of fastening contact р
3. azjem of an electrical wiring of ECU and wheel sensors (see. Onboard electric equipment);
4. Check the corresponding safety locks (see. Onboard electric equipment).

Recovery repair of ABS goes beyond qualification of the average amateur mechanic.

Reading and deleting of codes of malfunctions