ABS (Anti-lock Brake System)

Components and Components Location

COMPONENTS LOCATION

Description and Operation

Description

This specification applies to the hydraulic control unit (HCU) and the electronic control unit (ECU) of the hydraulic system and the electronic control unit (ECU).

This specification applies to the wiring as well as the installation of the ABS ECU.

This unit has the following functions.

• Wheel speed signal recording using the wheel speed sensors, installed on all 4 wheels.

• brake force monitoring

• safety function.

• self-diagnosis

• Interface for connecting an external diagnostic tool.

Installation location: Engine compartment

• The brake line length from the opening in the master cylinder to the HECU inlet port must not exceed 1 m.

• It must not be located near or under the engine block or wheel.

HOW IT WORKS

The ECU must start operating as soon as the operating voltage is supplied (IGN).

At the end of the initialization phase, the ECU must be operational.

During operation, the ECU must remain within the specified limits (voltage and temperature) in order to read the various signals from the different sensors and switches according to the control algorithm defined by the software, and to control the hydraulic and electrical actuators.

Wheel Sensor Signal Processing

The ECU must receive the rotational speed signal from the four active wheel speed sensors (RDKS).

After receiving the power supply, the wheel signals from the active wheel sensors are converted into a voltage signal by the signal conditioning circuit and sent to the MCU as an input signal.

solenoid valve control

When one side of the valve coil is connected to positive voltage, the valve relay is energized, and the other side is connected to ground through the semiconductor circuit, the solenoid valve starts operating.

The electrical function of the coils is constantly checked under normal operating conditions by the valve test pulse.

voltage limits

• overvoltage

  When overvoltage is detected (above 16.8 V), the ECU turns off both valve relays and the system is disabled.

  When the voltage returns to the normal operating range, the system returns to normal operation after the initialization phase.

• undervoltage

  When undervoltage is detected (below 9.3 V), ABS control is disabled and the warning lamp illuminates.

  When the voltage returns to the operating range, the warning lamp goes out and the ECU returns to normal operation.

Pump Motor Check

The ECU performs a pump motor check at 30 km/h after the ignition is switched on.

diagnostic interface

Faults detected by the ECU are encoded and stored in the ECU EEPROM, and are read by the diagnostic tool when the ignition is switched on.

The diagnostic interface can be used to check the ECU during production and to activate the HCU (drain line or roller and brake tester line).

WARNING LAMP MODULE

1. 1

   ABS WARNING LAMP

   The ABS warning lamp also indicates a self-check and an ABS malfunction. The ABS warning lamp illuminates:

   • during the initialization phase after the ignition is switched on (continuously for 3 seconds).

   • When the ABS function is disabled due to a fault.

   • In diagnostic mode.

   • When the ECU connector is disconnected from the ECU.

2. 2

   EBD/Parking Brake Warning Lamp

   The EBD warning lamp indicates a self-check as well as the EBD fault status. However, when the parking brake switch is turned on, the EBD warning lamp will remain illuminated at all times regardless of the EBD system operating condition. The EBD warning lamp illuminates:

   • during the initialization phase after the ignition is switched on (continuously for 3 seconds).

   • When the parking brake is applied or the brake fluid level is low.

   • When the EBD function is faulty.

   • In diagnostic mode.

   • When the ECU connector is disconnected from the ECU.

ABS CONTROL

1. 1

   NORMAL BRAKING without ABS

   	Inlet Valve (IV)	exhaust valve (OV)	return pump
   HOW IT WORKS	Open	close	Outside

   
   

   

2. 2

   HOLD MODE

   	Inlet Valve (IV)	exhaust valve (OV)	return pump
   HOW IT WORKS	close	Open	ON (engine speed control)

   
   

   

3. 3

   hold mode

   	Inlet Valve (IV)	exhaust valve (OV)	return pump
   HOW IT WORKS	close	close	ON (engine speed control)

   
   

   

4. 4

   Build pressure

   	Inlet Valve (IV)	exhaust valve (OV)	return pump
   HOW IT WORKS	Open	close	ON (engine speed control)

   
   

   

Schematic diagrams

Circuit diagram

TERMINAL DESCRIPTION