Toyota MR2 2000 Manual page 128

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
A6 (A), A7 (B) ABS ECU
(B)13–GROUND : Approx. 12 volts with the ignition SW at ON position
(B) 5–GROUND : Approx. 12 volts with the brake pedal depressed
(B)12, (B) 25–GROUND : Always continuity
: PARTS LOCATION
Code See Page
A2 30
A3 30
A6 A 32
A7 B 32
A12 A 34
A13 B 34
: RELAY BLOCKS
Code See Page
3 24
4 25
: JUNCTION BLOCK AND WIRE HARNESS CONNECTOR
Code See Page
6E
26 26
6H
: CONNECTOR JOINING WIRE HARNESS AND WIRE HARNESS
Code See Page
IC2
38 38
IC3
IF1 40
IG1
40 40
IG2
IJ1 40
120
Code
A14
A15
C10 A
C11 B
D1
E3
Relay Blocks (Relay Block Location)
R/B No.3 (Left Side of Instrument Panel)
R/B No.4 (Front Compartment Left)
Junction Block and Wire Harness (Connector Location)
Instrument Panel Wire and J/B No 6 (Instrument Panel Brace LH) Instrument Panel Wire and J/B No.6 (Instrument Panel Brace LH)
Joining Wire Harness and Wire Harness (Connector Location)
Engine Room Main Wire and Instrument Panel Wire (Left Kick Panel) Engine Room Main Wire and Instrument Panel Wire (Left Kick Panel)
Luggage Room Wire and Instrument Panel Wire (Instrument Panel Brace LH)
Luggage Room Wire and Instrument Panel Wire (Under the Instrument Panel Center) Luggage Room Wire and Instrument Panel Wire (Under the Instrument Panel Center)
Floor Wire and Instrument Panel Wire (Right Kick Panel)
See Page
34
34
32
32
32
34
2000 MR2 (EWD408U)
Code See Page
J2 33
J4 33
P7 35
S7 33