Page 9 of 4500

Fig. 5: ABS & TRACTION Actuator - Electronic Brake Force Distribution
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
Operation description
The skid control ECU receives the speed signal from each speed sensor to detect the slip condition
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560052004f004800510052004c004700110003[
The solenoid valve controls the oil pressure of each wheel cylinder and splits the control power
properly between the front and rear wheels and the right and rear wheels.
Both of the ABS warning lamp and the brake warning lamp come on to indicate a malfunction in
the EBD system.
c. BA (Brake Assist)
The primary purpose of the brake assist system is to provide an auxiliary brake force to assist the
driver who cannot generate a large enough brake force during emergency braking, thus helping to
maximize the vehicle's brake performance.
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Fig. 6: ABS & TRACTION Actuator - Brake Assist
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
Operation description
The skid control ECU receives the signal from the stop lamp switch and the oil pressure signal
from the master cylinder pressure sensor to determine whether brake assist is necessary or not. If
brake assist is deemed necessary, the 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 lamp comes on to indicate a malfunction in the brake assist system.
d. TRAC (Traction Control)
The TRAC system helps prevent the drive wheels from slipping if the driver presses down on the
accelerator pedal excessivel
y when starting off or accelerating on a slippery surface.
Page 11 of 4500
Fig. 7: ABS & TRACTION Actuator - Traction Control
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
Operation description
The skid control ECU detects vehicle's slip condition by receiving signals from the speed sensor
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vehicle position with suspension control ECU via CAN communication, and oil pressure with the
pump and solenoid valve. The SLIP indicator lamp blinks when the system is operating. TRAC
OFF switch stops traction control operation.
e. VSC (Vehicle Stability Control)
The VSC system helps prevent the vehicle from slipping sideways as a result of strong front wheel skid or
stron
g rear wheel skid during cornering.
Page 12 of 4500

Fig. 8: ABS & TRACTION Actuator - Vehicle Stability Control
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
Operation description
The skid control ECU determines vehicle condition by receiving signals from the speed sensor, yaw rate
and deceleration sensor and steering angle sensor. The skid control ECU controls engine torque with the
ECM, vehicle position with suspension control ECU via CAN communication, and oil pressure with the
pump and solenoid valve. The warning light comes on and the buzzer sounds when the system is
operating.
2.ABS with EBD & BA & TRAC & VSC OPERATION
a. Skid control ECU calculates vehicle stability tendency based on the signal of sensors, speed sensor,
yaw rate and deceleration sensor and steering angle sensor. And it judges whether the control of
engine output torque by electronic control throttle and of wheel brake pressure by brake actuator
will operate or not by the calculation results.
b. The SLIP indicator blinks and the VSC buzzer sounds to inform the driver that the VSC system is
operating. The SLIP indicator also blinks when TRAC is operating, and the operation being
performed is displayed.
3.FAIL SAFE FUNCTION
a. When a failure occurs in the ABS with BA & TRAC & VSC systems, the ABS warning light and
the VSC warning light turns on and the ABS with BA & TRAC & VSC operations are prohibited.
In addition to this, when there is a failure that disables the EBD operation, the brake warning light
also comes on and the EBD operation is prohibited (see FAIL
-SAFE CHART ).
b. If some control is prohibited due to a malfunction during it's operation, that control will be cut off
gradually not to change stability of vehicle suddenly.
4.PRE-COLLISION BRAKE ASSIST SYSTEM (w/ PRE-COLLISION BRAKE ASSIST SYSTEM)
Page 13 of 4500

If a collision (front collision) is determined to be unavoidable, the pre-collision brake assist system
receives the brake assist standby signal from the distance control ECU and enters brake assist standby
mode.
If the STP signal is input, the pre-collision brake assist system improves deceleration performance by
increasing pressure according to the amount of brake pedal effort.
The hand-held tester can be used at step 5, 8, 11, 14
1.Vehicle Brought to Workshop
2.(SEE CUSTOMER PROBLEM ANALYSIS CHECK
)
3.Check MULTIPLEX COMMUNICATION SYSTEM (SEE HOW TO PROCEED WITH
TROUBLESHOOTING )
DTC is output: Check MULTIPLEX COMMUNICATION circuit (SEE HOW TO PROCEED
WITH TROUBLESHOOTING )
There is no output: Go to step 4
4.(SEE CHECK CAN BUS LINE
)
DTC is output: Check CAN COMMUNICATION circuit (SEE SKID CONTROL ECU
COMMUNICATION STOP MODE )
There is no output: Go to step 5
5.Check and Clear DTCs (SEE DTC CHECK/CLEAR
)
6.Problem Symptom Confirmation
Symptom does not occur: Go to step 7
Symptom occurs: Go to step 8
7.Symptom Simulation (SEE ELECTRONIC CIRCUIT INSPECTION PROCEDURE
)
8.(SEE DTC CHECK/CLEAR
)
There is no output: Go to step 9
There is output: Go to step 10
9.(SEE PROBLEM SYMPTOMS TABLE
)
Check for fluid leakage and Go to step 10
Page 14 of 4500
10.(SEE DIAGNOSTIC TROUBLE CODE CHART )
11.Circuit Inspection (SEE DTC C0200/31 RIGHT FRONT SPEED SENSOR, DTC C0205/32 LEFT
FRONT SPEED SENSOR to TS AND CG TERMINAL CIRCUIT )
12.Identification of Problem
13.Repair
14.Confirmation Test
End
Page 15 of 4500
Fig. 9: ABS & EBD & BA Check Sheet
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
Page 16 of 4500
Fig. 10: TRAC & VSC Check Sheet