The car is equipped with ABS BOSCH 8.0
Depending on the vehicle equipment level, the BOSCH 8.0 system includes only ABS brakes or ABS combined with a trajectory stabilization system (CCT)
After carrying out any work on the stability control system, it is necessary to check the results of the repair during a road test, as well as using the diagnostic tool (CLIP).
Description of the ABS system with trajectory stabilization function
The ABS system consists of:
- - vacuum brake booster assembly with the main brake cylinder;
- – an electric pump assembly, including a hydraulic pump and a pressure control unit (12 solenoid valves);
- -ABS ECU;
- – pressure sensor;
- - steering wheel angle sensor built into the electric power steering;
- – combined sensor of angular and transverse acceleration;
- – four wheel speed sensors;
- – switch of the trajectory stabilization function.
The principle of operation of the ABS system with trajectory stabilization function
Optimum parameters are constantly calculated based on measurements of wheel speed and steering angle
These parameters reflect the optimal behavior of the car on the road.
They are compared with the real parameters of the car movement based on measurements of the speed of angular and lateral accelerations
When a deviation of the real trajectory from the optimal one is detected, the corresponding wheel is braked
In some cases, in case of insufficient controllability, the system brakes both wheels at the same time.
The moment of forces created in this way returns the car to the optimal trajectory.
In some cases, the system (when the traction control function is activated) changes the engine torque.
Features of the trajectory stabilization system
The trajectory stabilization system function can be disabled by a switch located on the dashboard.
The system cannot be disabled if the speed exceeds the threshold of 50 km/h.
The system is automatically reactivated when the ignition is switched on or if the speed exceeds 50 km/h.
The ABS electric pump assembly is equipped with an ECU with a 26-pin connector (fig. 1).
The electric pump unit of the trajectory stabilization system and the ABS system is equipped with an ECU with a 46-pin connector (Fig. 2).
The ECU forms one unit with the electric pump assembly.
The following modes of operation of the anti-lock braking system are distinguished:
- — normal braking mode.
During normal braking, the solenoid valve is de-energized, the inlet valve is open, the outlet valve is closed
When you press the brake pedal, pressurized brake fluid is supplied to the working cylinder through the solenoid valve and actuates the wheel brakes
When the brake pedal is released, the brake fluid returns to the brake master cylinder through the inlet and check valves;
- — emergency braking mode.
If the wheel locks up during emergency braking, the module issues a command to the solenoid valve to reduce the supply of brake fluid, then voltage is applied to each solenoid valve
The inlet valve closes and the brake fluid supply from the master cylinder is shut off; the outlet valve opens, and the brake fluid flows from the working cylinder to the master cylinder, and then to the reservoir, which causes a decrease in pressure;
- — pressure maintenance mode.
When the pressure in the working cylinder decreases to the maximum, the module issues a command to the solenoid valve to maintain brake fluid pressure, voltage is applied to the inlet valve and not to the outlet valve.
At the same time, the inlet and outlet valves are closed and the brake fluid does not leave the working cylinder;
- — pressure increase mode.
If the module detects that the wheel is not locked, it de-energizes the solenoid valve.
The solenoid valves are not energized, the brake fluid enters the working cylinder through the inlet valve, the pressure in which increases.
To diagnose and repair the anti-lock brake system, special equipment and equipment are required, therefore, in case of failure, contact a specialized service station.