Toyota 2004 CELICA Electric Troubleshooting Manual page 155

ABS
SYSTEM OUTLINE
This system controls the respective brake fluid pressures acting on the brake cylinders of the right front wheel, the left front
wheel, the right rear wheel and the left rear wheel when the brakes are applied in a panic stop so that the wheels do not lock.
This results in improved directional stability and steerability during panic braking.
1. INPUT SIGNALS
(1) Speed sensor signal
The speed of the wheels is detected and input to TERMINALS FL+, FR+, RL+ and RR+ of the ABS ECU.
(2) Stop light SW signal
A signal is input to TERMINAL STP of the ABS ECU when the brake pedal depressed.
2. SYSTEM OPERATION
During sudden braking the ABS ECU which has signals input from each of the sensor, controls current to the solenoid inside
the actuator and causes the hydraulic pressure acting on each of the wheel cylinder escape to the reservoir. The pump
inside the actuator is also operating at this time and it returns the brake fluid from the reservoir to the master cylinder,
preventing locking of the vehicle wheels.
If the ECU judges that the hydraulic pressure acting on the wheel cylinder is insufficient, the current acting on the solenoid is
controlled and the hydraulic pressure is increased. Holding of the hydraulic pressure is also controlled by the ECU, by the
same method as above. By repeated pressure reduction, holding and increase are repeated to maintain vehicle stability and
to improve steerability during sudden braking.
SERVICE HINTS
S11 SKID CONTROL ECU WITH ACTUATOR
1, 23-GROUND : Always approx. 12 volts
2, 24-GROUND : Always continuity
25-GROUND : Approx. 12 volts with the ignition SW at ON position
10-GROUND : Approx. 12 volts with the brake pedal depressed
: PARTS LOCATION
Code
32 (1ZZ-FE)
A6 A6
34 (2ZZ-GE)
32 (1ZZ-FE)
A7 A7
34 (2ZZ-GE)
A15 38
: JUNCTION BLOCK AND WIRE HARNESS CONNECTOR
Code See Page
IF
IG
II
25
IK
IM
2D
23 23
2G
: CONNECTOR JOINING WIRE HARNESS AND WIRE HARNESS
Code See Page
IE3 44
IG3 46
II2 46
: GROUND POINTS
Code See Page
40 (1ZZ-FE)
EB EB
42 (2ZZ-GE)
IF 44
156
See Page Code
A16
C12
C13
D1
P3
Junction Block and Wire Harness (Connector Location)
Instrument Panel Wire and Instrument Panel J/B (Instrument Panel Brace RH)
Engine Room Main Wire and Engine Room J/B (Engine Compartment Left) Engine Room Main Wire and Engine Room J/B (Engine Compartment Left)
Joining Wire Harness and Wire Harness (Connector Location)
Engine Room Main Wire and Instrument Panel Wire (Instrument Panel Brace LH)
Engine Room No.2 Wire and Instrument Panel Wire (Right Kick Panel)
Engine Room Main Wire and Floor Wire (Instrument Panel Brace LH)
Ground Points Location
Front Left Fender Front Left Fender
Instrument Panel Brace RH
See Page
38
A 36
B 36
36
37
(
2004 CELICA (EWD538U)
Code See Page
S8 37
32 (1ZZ-FE)
S11 S11
34 (2ZZ-GE)
)