brake fluid TOYOTA RAV4 2006 Service Owner's Manual

BRAKE CONTROL – VEHICLE STABILITY CONTROL SYSTEMBC–7
BC
(b) EBD (Electronic Brake Force Distribution):
The EBD control utilizes the ABS to create the
proper brake force distribution between the front
and rear wheels in accordance with the driving
conditions and vehicle load. In addition, when the
brakes are applied while cornering, it also controls
the braking forces of the right and left wheels,
helping to maintain vehicle stability.
(1) Operation description:
The skid control ECU receives speed signals
from each speed sensor to detect the slip
conditions of the wheels and sends control
signals to the solenoid.
The solenoid valve controls the brake fluid
pressure of each wheel cylinder and divides the
control power properly between the front and
rear wheels and the right and left wheels.
The brake warning light comes on to indicate
malfunctions in the EBD system.
C115100E05

BC–8BRAKE CONTROL – VEHICLE STABILITY CONTROL SYSTEM
BC
(c) BA (Brake Assist):
The primary purpose of the brake assist system is to
provide auxiliary brake force to assist drivers who
cannot generate a large enough brake force during
emergency braking, thus helping to maximize the
vehicle's braking performance.
(1) Operation description:
The skid control ECU receives speed signals
from each speed sensor and the fluid pressure
signal from the master cylinder pressure sensor
to determine whether brake assist is necessary.
If brake assist is deemed necessary, the skid
control ECU sends control signals to the pump
motor and solenoid. The pump and the solenoid
valve then control the pressure applied to each
wheel cylinder. The ABS warning light comes on
to indicate malfunctions in the BA (brake assist)
system.
w/ 16-inch disc: The brake warning light and
ABS warning light come on to indicate
malfunctions in the BA system.
C135908E01

BC–10BRAKE CONTROL – VEHICLE STABILITY CONTROL SYSTEM
BC
(1) Operation description:
The skid control ECU detects the vehicle's slip
condition by receiving signals from each speed
sensor and the ECM via CAN communication.
The skid control ECU controls engine torque
with the ECM via CAN communication and
brake fluid pressure through the pump and
solenoid valve. The slip indicator light blinks
when the system is operating.
for 4WD: The VSC warning light comes on when
the TRC system malfunctions.
for 2WD: The VSC warning light and SLIP
indicator light comes on when the TRC system
malfunctions.

BC–12BRAKE CONTROL – VEHICLE STABILITY CONTROL SYSTEM
BC
(1) Operation description:
The skid control ECU determines the vehicle
condition by receiving signals from the speed
sensor, the yaw rate and deceleration sensor
and the steering sensor. The skid control ECU
controls engine torque with the ECM via CAN
communication and brake fluid pressure through
the pump and solenoid valve. The slip indicator
light blinks and the skid control buzzer sounds
when the system is operating.
for 4WD: The VSC warning light comes on when
the TRC system malfunctions.
for 2WD: The VSC warning light and slip
indicator light come on when the TRC system
malfunctions.
(f) Downhill Assist Control:
When the downhill assist control switch is pressed
with the shift lever on L or R range and the
accelerator and brake pedals not depressed,
downhill assist control is activated. When activated,
4-wheel hydraulic pressure control occurs in order
to maintain a constant low vehicle speed without
causing the wheels to become locked. Thus, the
vehicle can descend a steep hill in a stable manner.
HINT:
• Depressing the accelerator and brake pedal
cancels control of the downhill assist control.
• Downhill assist control begins operating when
driving down on a slope at a speed of 25 km/h
(16 mph) or less with the engine brake applied.

BC–14BRAKE CONTROL – VEHICLE STABILITY CONTROL SYSTEM
BC
(g) Hill-start assist control:
When the vehicle starts off on a steep hill, hill-start
assist control effects 4-wheel hydraulic pressure
control to prevent the vehicle from rolling
backwards.
After a maximum of 2 seconds after the control has
started, fluid pressure is gradually released and
control will be complete.
HINT:
• Depressing the brake pedal cancels control of
the hill-start assist control.
• Hill-start assist control does not operate when
the shift lever is in the P position, or when the
vehicle is running, the parking brake lever is set,
or the accelerator pedal is depressed.
C132095E01

BC–18BRAKE CONTROL – VEHICLE STABILITY CONTROL SYSTEM
BC
(3) Front Wheel Skid Tendency
When the skid control ECU determines that
there is a front wheel skid tendency, it controls
the VSC to dampen the front wheel skid. At the
same time, it effects cooperative control with the
EPS to provide steering torque assist, which
facilitates the driver's steering maneuvers to
stabilize the vehicle posture. To prevent
excessive steering maneuvers, it provides a
steering torque assist. This assist increases the
resistance to counter the driver's steering effort,
if the driver turns the steering wheel excessively.
(4) Rear Wheel Skid Tendency
When the skid control ECU determines that
there is a rear wheel skid tendency, it controls
the VSC to dampen the rear wheel skid. At the
same time, it effects cooperative control with the
EPS to provide steering torque assist, which
facilitates the driver's steering maneuvers in the
direction to correct the rear wheel skid.
(5) Acceleration During Cornering
A sudden acceleration of the vehicle during
cornering may cause a drive wheel to freewheel,
which could cause the front wheels or rear
wheels to skid. If the skid control ECU
determines that there is freewheeling of a drive
wheel, a front wheel skid tendency, or a rear
wheel skid tendency, it effects cooperative
control with the 4WD system to optimally control
the drive torque distribution to the front and rear
wheels. Furthermore, it controls the TRC and
the VSC as needed to ensure driving stability
and acceleration performance.
(b) Operation
The operation of the solenoid valves under the
cooperative control is the same as the TRC or VSC
operation.
3. ABS WITH EBD, BA, TRC AND VSC OPERATION
(a) The skid control ECU calculates vehicle stability
tendency based on the signals from the 4 wheel
speed sensors, the yaw rate and deceleration
sensor and the steering sensor. In addition, it
evaluates the results of the calculations to
determine whether any control actions (control of
the engine output torque by electronic throttle
control and of the brake fluid pressure by the ABS
and TRACTION actuator) should be implemented.
(b) The slip indicator blinks and the skid control buzzer
sounds to inform the driver that the VSC system is
operating. The slip indicator also blinks when
traction control is operating, and the operation being
performed is displayed.

BRAKE CONTROL – VEHICLE STABILITY CONTROL SYSTEMBC–19
BC
4. FAIL SAFE FUNCTION
(a) When a failure occurs in the ABS with BA, TRC and
VSC systems, the ABS and VSC warning lights
illuminate, the slip indicator light comes on*1 or
remains off*2, and the operations of those systems
are prohibited. In addition to this, when a failure
which disables the EBD operation occurs, the brake
warning light comes on and its operation is
prohibited.
HINT:
*1: for 2WD
*2: for 4WD
(b) If control is prohibited due to a malfunction during
operation, control is disabled gradually to avoid
sudden vehicle instability.
5. INITIAL CHECK
(a) When the vehicle speed first reaches approximately
6 km/h (4 mph) or more after the ignition switch is
turned ON, each solenoid valve and the motor of the
ABS and TRACTION actuator are sequentially
activated to perform electrical checks. During the
initial check, the operating sound of the solenoid
valve and motor can be heard from the engine
compartment, but this does not indicate a
malfunction.
6. SERVICE MODE
(a) VSC operation can be disabled by operating the
intelligent tester.
HINT:
Refer to the intelligent tester operator's manual for
further details.
7. FUNCTION OF COMPONENTS
Components Functions
Speed Sensor
(Semiconductor Type)Detects the wheel speed and sends the signal to skid
control ECU
Skid Control ECU
(Housed in ABS and TRACTION Actuator)• Processes the signals from each sensor to control the
ABS, BA, TRC, and VSC
• Sends and receives control signals to and from the
ECM, yaw rate and deceleration sensor, steering
sensor, etc. via CAN communication.
ABS and TRACTION Actuator • Consists of the master cylinder cut solenoid valve,
holding solenoid valve, pressure reduction solenoid
valve, pump motor, and reservoir, and adjusts the brake
fluid pressure applied to each wheel cylinder
• Houses the skid control ECU
Solenoid Relay • Supplies power to each solenoid
• Housed in the skid control ECU
Motor Relay (VSC MTR Relay) • Supplies power to the pump motor
• Installed in engine room No. 1 relay block
Fail-safe Relay (VSC FAIL Relay) • Cuts off power to the motor when the pump motor circuit
malfunctions
• Installed in engine room No. 1 relay block

BC–20BRAKE CONTROL – VEHICLE STABILITY CONTROL SYSTEM
BC
HINT:
*1: w/ Downhill assist control
*2: for 2WD w/ AUTO LSD
Steering Sensor • Detects the steering extent and direction and sends
signals to the skid control ECU via CAN communication
• Has a magnetic resistance element which detects the
rotation of the magnet housed in the detection gear in
order to detect the changes in magnetic resistance and
the steering amount and direction
Yaw Rate and Deceleration Sensor • Yaw rate sensor detects the vehicle's angular velocity
(yaw rate) in the vertical direction based on the extent
and direction of the deflection of the piezoelectric
ceramics
• Deceleration sensor measures the capacity of the
condenser that changes the distance between the
electrodes depending on G force, which occurs when
the vehicle is accelerated, and converts the measured
value into electrical signals
• Sends signals to the skid control ECU via CAN
communication
Master Cylinder Pressure Sensor • Detects the brake fluid pressure in the master cylinder
• Housed in the ABS and TRACTION actuator
ECM• Controls the engine output when TRC and VSC are
operating with the skid control ECU via CAN
communication
Downhill Assist Control switch*1 Allows the driver to turn downhill assist control ON and OFF
AUTO LSD switch*2 Allows the driver to turn AUTO LSD ON and OFF
Combination Meter ABS Warning Light • Illuminates to inform the driver that a malfunction in the
ABS has occurred
• Blinks to indicate DTCs that relate to the ABS
VSC Warning Light • Illuminates to inform the driver that a malfunction in the
VSC system has occurred
• Blinks to indicate DTCs that relate to the VSC
Brake Warning light • Illuminates to inform the driver that the parking brake is
ON when the system is normal, and when the brake
fluid has decreased
• Illuminates to inform the driver that a malfunction in the
EBD has occurred
Slip Indicator Light • Blinks to inform the driver that TRC, VSC, downhill
assist control and hill-start assist control are operating
• Illuminates to inform the driver that a malfunction has
occurred in the TRC or VSC system
AUTO LSD Indicator Light*2 Lights up to inform the driver when AUTO LSD operation is
possible
Downhill Assist Control Indicator
Light*1Lights up to inform the driver when downhill assist control
operation is possible
Skid Control Buzzer • Intermittently sounds to inform the driver that the VSC is
operating
• Housed in the combination meter Components Functions

BC–22BRAKE CONTROL – VEHICLE STABILITY CONTROL SYSTEM
BC
Result
B
A
Result
B
A
Result
B
A
(a) Terminals of ECU (see page BC-41)
(b) Data List / Active Test (see page BC-52)
NEXT
NEXT
Result Proceed to
DTC is not output A
DTC is output B
Go to CAN COMMUNICATION SYSTEM
7CHECK FOR DTC*
Result Proceed to
DTC is not output A
DTC is output B
Go to step 10
8PROBLEM SYMPTOMS TABLE
Result Proceed to
Fault is not listed in problem symptoms table A
Fault is listed in problem symptoms table B
Go to step 10
9OVERALL ANALYSIS AND TROUBLESHOOTING
Go to step 11
10CHECK FOR FLUID LEAKAGE

BRAKE CONTROL – VEHICLE STABILITY CONTROL SYSTEMBC–49
BC
• *4: w/ 16-inch disc
• The DTCs can be read by connecting SST (09843-
18040) between the TC and CG terminals of the
DLC3 and observing the blinking pattern of the ABS
and VSC warning lights, or by using an intelligent
tester (see page BC-47).
• This system has a sensor signal check function (see
page BC-28).
2. CHECK WARNING LIGHT AND INDICATOR LIGHT
(a) Release the parking brake lever.
NOTICE:
Before releasing the parking brake lever, set
chocks to hold the vehicle for safety.
HINT:
When the parking brake is applied or the brake fluid
level is low, the brake warning light comes on.
(b) When the ignition switch is turned ON, check that
the ABS, VSC and brake warning lights and the slip,
downhill assist control and AUTO LSD indicator
lights come on and go off in about 3 seconds.
HINT:
If the warning lights do not illuminate, confirm
whether the bulbs have burned out, and also check
for CAN communication system DTCs, since the
skid control ECU and combination meter are
connected by the CAN communication line.
If the warning light remains on, perform relevant
troubleshooting procedures. The relevant
troubleshooting procedures are in the sections listed
in the table below.
C132117E03
Section Title See procedure
ABS Warning Light Remains ONBC-134