Hyundai Tiburon (2003 year). Manual - part 83

This specification applies to Hydraulic and Electronic Control Unit (HECU) of the Anti lock Braking System(ABS) and
Traction Control System(TCS).
This HECU has the functions as follows:

The HECU shall be put into operation by switching on the operating voltage (IGN).
On completion of the initialization phase, the HECU shall be ready for operation.
In the operating condition, the HECU 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.
The HECU shall receive wheel speed signal from the four inductive wheel sensors.
The wheel signals are converted to square wave by the signal conditioning circuit and given as input to the

- processor.

The sensor connections shall be monitored for short-circuit and inter-ruption and then in the event of 2 sensor failures, the
HECU shall shut down the system.
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 MOSFET, the solenoid valve goes into operation.
The electrical function of the valves are always monitored by the valve test pulse under normal operation conditions.
When overvoltage is detected(above 16V), the HECU 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.
In the event of undervoltage(below 10V), 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 the HECU returns to normal operating
mode.
The pump motor operates when the ABS is functioning.
The HECU performs a pump motor test at a speed of 20km/h once after turned the Ignition switch on. You may hear the
motor operate at this time, but it is normal.
Malfunctions or failures detected by the HECU are encoded on the HECU, stored in a EEPROM and read out by diagnostic
equipment (hi-scan pro) when the ignition switch is turned on.

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and Operation

DESCRIPTION

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

- Control of braking force and traction force

- Failsafe function

- Self diagnosis function

- Interface with the external diagnosis tester

Operation

Warning lamp control

1. ABS warning lamp module

The ABS warning lamp module indicates the operating condition of the ABS.
The ABS warning lamp is turned on under the following conditions.

A. During the initialization phase after ignition switch ON (3 seconds).

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

C. When the system ECU is shut down even though ignition power is applied.

D. During diagnostic mode.

E. When the HECU connector is disconnected.

2. EBD warning lamp module

The EBD warning lamp module indicates the operating condition 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 is turned on under the following conditions.

A. During the initialization phase after ignition switch ON. (3 seconds).

B. When the system ECU is shut down even though ignition power is applied.

C. When the parking brake switch is ON or brake fluid is low level.

D. In the event of inhibition of EBD functions by failure.

3. TCS lamp module

The TCS warning lamp module indicates the operating condition of the TCS.
The TCS warning lamp is turned on under the following conditions:

TCS function lamp is turned on when the TCS functions are operating (Blinking-2Hz).

A. During the initialization phase after ignition switch ON (3 seconds).

B. In the event of inhibition of TCS functions by failure.

C. When the TCS OFF switch is turned on.

Diagnostic trouble code (DTC)

1. If the CPU cannot be activated or the CPU fails, the ABS indicator comes on, but the DTC is not memorized.

2. The memory can hold any number of DTCs. However, when the same DTC is detected more than once, the later one is

written over the old one.
Therefore, when the same problem is detected repeatedly, it is memorized as one DTC.

3. The DTCs are indicated in the order they occur.

4. The DTCs are memorized in the EEPROM (non - volatile memory). Therefore, the memorized DTCs cannot be

canceled by disconnecting the battery. Perform the specified procedures to erase the DTCs.

Self-diagnosis

1. Self diagnosis can be classified into two categories:

A. Initial diagnosis:

Performed right after the engine starts and until the ABS indicator goes off.

B. Regular diagnosis:

Performed right after the initial diagnosis until the ignition switch is turned OFF.

2. When a problem is detected by self-diagnosis, the system:

A. Turns the solenoid valve OFF

B. Turns the pump motor OFF

C. Turns the ABS indicator ON

How to troubleshoot ABS DTC

1. Question the customer about the conditions when the problem occured, and try to reproduce the same conditions for

troubleshooting. Find out when the ABS indicator came on, such as during initial diagnosis, during ABS control, after
ABS control, when vehicle speed was at a certain speed, etc.

2. When the ABS indicator does not come on during the test-drive, but troubleshooting is performed based on the DTC.

check for loose connectors, poor contact of the terminals, etc. before you start troubleshooting.

3. After troubleshooting, erase the DTC and test-drive the vehicle. Be sure the ABS indicator does not come on.

HI-SCAN (PRO) CHECK

1. Turn the ignition switch OFF.

2. Connect the Hi-scan (pro) to the 16P data link connector located underneath the lower crash pad panel.

ABS OPERATION

3. Turn the ignition switch ON.

4. Check for diagnostic trouble codes using the Hi-scan (pro).

5. After completion of the repair or correction of the problem, erase the stored fault codes using the clear key on the Hi-

scan (pro).

6. Disconnect the Hi-scan (pro) from the 16P data link connector.

SYSTEM FUNCTION

1. NORMAL BRAKING

Solenoid valve

State

Valve

Passage

Pump motor

IN (NO)

OFF

OPEN

Master cylinder Wheel cylinder

OFF

OUT (NC)

OFF

Wheel cylinder Reservoir

Under the normal braking, voltage is not supplied to solenoid valve, inlet valve is opened and outlet valve is closed.
When the brake is depressed, brake fluid is supplied to the wheel cylindervia solenoid valve to activate the brake.
When the brake is released, brake fluid is back to the master cylinder via inlet valve and check valve.

2. DUMP MODE

Solenoid valve

State

Valve

Passage

Pump motor

IN (NO)

Master cylinder Wheel cylinder

OUT (NC)

OPEN

Wheel cylinder Reservoir

Under the emergency braking, if the wheels start to lock up, HECU sends a signal to the solenoid valve to decrease
the brakefluid, then voltage is supplied to each solenoid. At this time inlet valve is closed and brake fluid is blocked
from the mastercylinder. Conversely outlet valve is opened and brake fluid passes through wheel cylinder to reservoir,
resulting in pressure decrease.

3. HOLD MODE

Solenoid valve

State

Valve

Passage

Pump motor

IN (NO)

Master cylinder Wheel cylinder

OUT (NC)

OFF

Wheel cylinder Reservoir

When the brake fluid pressure is maximally decreased in wheel cylinder, HECU sends a signal to solenoid valve to
keep the fluidpressure, voltage is supplied to inlet valve but it is not supplied to outlet valve. At this time inlet and outlet
valves are closed and brake fluid is kept in wheel cylinder.

4. INCREASE MODE

Solenoid valve

State

Valve

Passage

Pump motor

IN (NO)

OFF

OPEN

Master cylinder Wheel cylinder

OUT (NC)

OFF

Wheel cylinder Reservoir

If HECU determines there's no lock-up in the wheel, HECU cuts voltage to solenoid valve. So voltage is not supplied
to each solenoid valve, brake fluid passes through the inlet valve to wheel cylinder, resulting in pressure increase.

TRACTION CONTROL SYSTEM (TCS) OPERATION

1. NORMAL MODE

Solenoid valve

State

Valve

Motor pump

TC valve

IN (NO)

OFF

OPEN

OFF

OUT (NC)

OFF

• In the normal driving condition, TC valve (normally open) is the passage between the master cylinder and the each

wheel cylinder.

• When brake pedal is applied, brake pressure is delivered to the wheel cylinders via NO-TC valve and all solenoid

valves inside the hydraulic unit are deactivated.

• In case of TCS malfunction it does not affect brake operation.

2. PRESSURE INCREASE MODE

Solenoid valve

State

Valve

Motor pump

TC valve

IN (NO)

FRONT: OFF

REAR: ON

FRONT: OPEN

REAR: CLOSE

OUT (NC)

OFF

• If a front wheel spin is detected, TCS begins a brake control to decrease a wheel spin.

• Hydraulic shuttle valve (HSV) is opened.

Brake fluid is supplied from the master cylinder by motor operation to the spin wheel via HSV.

• TC valve is closed (ON).

Brake pressure generated from motor pump is delivered only to the front wheel.

• Inlet valve remains open to deliver the brake pressure generated from motor pump to the spinning wheels.

3. PRESSURE DUMP MODE

Solenoid valve

State

Valve

Motor pump

TC valve

IN (NO)

OUT (NC)

FRONT: ON

REAR: OFF

FRONT: OPEN

REAR: CLOSE

• When the wheel deceleration is under the threshold and the wheel spin is reduced under a slip threshold, applied

brake pressure is reduced to get a optimum traction force.

• Outlet valve is open to release the brake pressure and inlet valve is closed to block the pressure increase from the

motor pump.

• Hydraulic shuttle valve (HSV) remains opened, TC valve is ON.

• Motor is ON, to dump the brake fluid being released from the lock-up wheel.

4. PRESSURE HOLD MODE

Solenoid valve

State

Valve

Motor pump

TC valve

IN (NO)

OUT (NC)

OFF

TRACTION CONTROL SYSTEM (TCS) FUNCTION

1. Main performance

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