Hyundai Accent: ABS(Anti-Lock Brake System) / Description and Operation

- Description This specification applies to HCU (Hydraulic Control Unit) and ECU (Electronic Control Unit) of the HECU. (Hydraulic and Electronic Control Unit)This specification is for the wiring design and installation of ABS ECU.This unit has the functions as follows.

– Input of signal from the wheel speed sensors attached to each wheel.

– Control of braking force.

– Failsafe function.

– Self diagnosis function.

– Interface with the external diagnosis tester.

Installation Position : Engine Compartment

– Brake tube length from Master cylinder port to HECU inlet port should be max. 1m

– The position should not be close to the engine block and not lower than the wheel.

Operation The ECU shall be put into operation by switching on the operating voltage (IGN).On completion of the initialization phase, the ECU shall be ready for operation.In the operating condition, the ECU shall be ready, within the specified limits (voltage and temperature), to process the signals offered by the various sensors and switches in accordance with the control algorithm defined by the software and to control the hydraulic and electrical actuators.Wheel Sensor Signal Processing The ECU shall receive wheel speed signal from the four active wheel sensors.The wheel signals are converted to voltage signal by the signal conditioning circuit after receiving current signal from active wheel sensors and given as input to the MCU.Solenoid Valve Control When one side of the valve coil is connected to the positive voltage that is provided through the valve relay and the other side is connected to the ground by the semiconductor circuit, the solenoid valve goes into operation.The electrical function of the coils are always monitored by the valve test pulse under normal operation conditions.Voltage Limits

– OvervoltageWhen overvoltage is detected(above 16.8 V), the ECU switches off the valve relay and shuts down the system.When voltage is returned to operating range, the system goes back to the normal condition after the initialization phase.

– UndervoltageIn the event of undervoltage(below 9.3 V), ABS control shall be inhibited and the warning lamp shall be turned on.When voltage is returned to operating range, the warning lamp is switched off and ECU returns to normal operating mode.

Pump Motor Checking The ECU performs a pump motor test at a speed of 30km/h once after IGN is switched on.Diagnostic Interface Failures detected by the ECU are encoded on the ECU, stored in a EEPROM and read out by diagnostic equipment when the ignition switch is turned on.The diagnosis interface can also be used for testing the ECU during production of the ECU and for actuating the HCU (Air-bleeding line or Roll and Brake Test line).Warning Lamp Module [Super Vision]

[General]

1.ABS Warning LampThe active ABS warning lamp indicates the selftest and failure status of the ABS. The ABS warning lamp shall be on :

– During the initialization phase after IGN ON. (continuously 3 seconds).

– In the event of inhibition of ABS functions by failure.

– During diagnostic mode.

– When the ECU Connector is separated from ECU.

2.EBD/Parking brake Warning LampThe active EBD warning lamp indicates the selftest and failure status of the EBD. However, in case the Parking Brake Switch is turned on, the EBD warning lamp is always turned on regardless of EBD functions.The EBD warning lamp shall be on:

– During the initialization phase after IGN ON. (continuously 3 seconds).

– When the Parking Brake Switch is ON or brake fluid level is low.

– When the EBD function is out of order.

– During diagnostic mode.

– When the ECU Connector is separated from ECU.

- ABS Control

1.Normal Braking without ABS

	Inlet valve (IV)	Outlet valve (OV)	Return pump
Operation	Open	Close	OFF

   

• IV : Inlet Valve

• OV : Outlet Valve

• RL : Rear left wheel

• FR : Front right wheel

• FL : Front left wheel

• RR : Rear right wheel

• RP : Return pump

2.Decrease Mode

	Inlet valve (IV)	Outlet valve (OV)	Return pump
Operation	Close	Open	ON (Motor speed control)

   

• IV : Inlet Valve

• OV : Outlet Valve

• RL : Rear left wheel

• FR : Front right wheel

• FL : Front left wheel

• RR : Rear right wheel

• RP : Return pump

3.Hold Mode

	Inlet valve (IV)	Outlet valve (OV)	Return pump
Operation	Close	Close	ON (Motor speed control)

   

• IV : Inlet Valve

• OV : Outlet Valve

• RL : Rear left wheel

• FR : Front right wheel

• FL : Front left wheel

• RR : Rear right wheel

• RP : Return pump

4.Increase Mode

	Inlet valve (IV)	Outlet valve (OV)	Return pump
Operation	Open	Close	ON (Motor speed control)

   

• IV : Inlet Valve

• OV : Outlet Valve

• RL : Rear left wheel

• FR : Front right wheel

• FL : Front left wheel

• RR : Rear right wheel

• RP : Return pump