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6) HSA (Hill Start Assist)
The HSA (Hill Start Assist) prevents the vehicle from rolling backward by supplying the hydraulic
pressure to the wheels by the HECU after the brake pedal is released when starting off on uphill.
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7) Emergency Hazard Flasher Control (Coupled with ABS)
(1) System layout
(2) Emergency stop signal function
When ABS system is operating (or sudden braking), the hazard warning flashers will blink for 10
seconds to inform the emergency situation to the vehicles behind.
(3) Operating process
When receiving the emergency stop signal through PCAN communication it blinks with the interval of 4
Hz and when receiving the emergency stop OFF signal through PCAN communication it blinks with the
interval of 1.25 Hz, normal operating speed.
However, the manual operation of the switch has a priority over this function.
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flasher
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The BCM flashes the emergency auto hazard flasher with interval of 1.25 times/sec.:
The emergency hazard flasher does not operate if the vehicle speed is over 50 km/h when the
emergency stop signal is received.
The emergency hazard flasher operates if the vehicle speed is 50 km/h or lower when the
emergency stop signal is received.
When vehicle speed increases more than 10 km/h above the speed when the signal is received
during operation by emergency braking signal, the emergency hazard flasher stops operation.
When turning emergency hazard flasher switch OFF during operation by emergency braking signal,
it stops operation.
It is deactivated automatically 10 seconds after if items 2) and 3) above are not met during operation
by emergency braking signal.
If multi-function automatic hazard flasher signal is received during operation by emergency braking
signal, it will be overridden. -
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6. HYDRAULIC CIRCUIT OF ESP
MCP: Master Cylinder Primary
MSP: Master Cylinder Secondary
ESV: Electric Shuttle Valve
NO: Normal Open
NC: Normal Close
LPA: Low Pressure Accumulator
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Circuit description ▶
When compared to the vehicle equipped with ABS/EBD only, the internal hydraulic circuit has a
normally-open separation valve and a shuttle valve in primary circuit and in secondary circuit.
When the vehicle brakes are not applied during engine running or when applying the non-ABS operating
brakes, the normally-open separation valve and the inlet valve are open, whereas the normally-closed
shuttle valve and the outlet valve are closed.
When the ESP system is operating, the normally-open separation valve will be closed by the solenoid
valve operation and the hydraulic circuit will be established by the shuttle valve. Then, the inlet and outlet
valves will be closed or open depending on the braking pressure RISE, HOLD or DUMP conditions.
Flashing warning lamp and warning sound during ESP operation ▶
When the ESP operates while the vehicle is moving, the ESP warning lamp on the instrument panel
flickers and the buzzer sounds at every 0.1 second. The ESP lamp operation is to inform a driver that the
vehicle is extremely unstable.
The ESP system is just a supplementary system for the vehicle and it cannot control the vehicle over the
physical limit. Do not solely rely on the system but be advised to drive the vehicle safely.
Drive feeling during ESP operation ▶
When the ESP system activates, the driving feeling can be different depending on vehicle driving
conditions. For example, it will feel different when the ESP system is activated while the ABS is operated
by depressing the brake pedal and when the ESP system is in control without the brake pedal
depressed on the same curve.
If the ESP system operates with the brake applied, the brake pressure will be increased on the
corresponding wheel which already has braking pressure for the ESP controls. In other words, the ESP
system would make the driver feel more abruptly braked compared to the situation that the braking
pressure is applied to wheel which had no braking force.
Noise and vibration that driver senses during ESP operation ▶
The ESP system may transfer noise and vibration to a driver due to the pressure changes caused by the
motor and valve operations in a very short period of time.
Extreme cornering will trigger the ESP operation and this will make the driver sense noise and vibration
due to sudden brake application.
Also, the ESP system controls the engine power. Therefore, the driver may notice the engine power
decreases even when the accelerator pedal is depressed.
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1) Idling and Normal Braking Condition
In this position, the separation valve and the inlet valve are open (normal open), the electrically operated
shuttle valve and the outlet valve are closed.
When the brake is applied under these conditions, the brake fluid will be sent to each wheel via the
separation valve and inlet valve.
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2) DUMP (ESP is working) Mode
The pressure decreases just before the wheel speed drops and the wheels are locked.
The inlet valve closes and the outlet valve opens as in the ABS HECU and the oil is gathered at the low
pressure chamber while no additional oil is being supplied. Then the pump operates to allow fast oil
drainage. The shuttle valve and the separation valve do not operate while decompression.
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3) HOLD (ESP is working) Mode
The Inlet valve and outlet valve will be closed to maintain the pressure in the hydraulic circuit applied at
the wheels. By closing the valves, the hydraulic pressure at the wheels will not be lost or supplied any
more. During ESP operation, the separation valve closes and only the shuttle valve at the pump opens.