Toyota 1993 MR2 Wiring Diagrams page 145

ABS (ANTI–LOCK BRAKE SYSTEM)
SYSTEM OUTLINE
THIS SYSTEM CONTROLS THE RESPECTIVE BRAKE FLUID PRESSURES ACTING ON THE DISC BRAKE CYLINDERS OF THE RIGHT
FRONT WHEEL, LEFT FRONT WHEEL AND REAR WHEELS, 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 IS OPERATED.
(3) PARKING BRAKE SW SIGNAL
A SIGNAL IS INPUT TO TERMINAL PKB OF THE ABS ECU WHEN THE PARKING BRAKE IS OPERATED.
2. SYSTEM OPERATION
DURING SUDDEN BRAKING THE ABS ECU, WHICH HAS SIGNALS INPUT FROM EACH SENSOR, CONTROLS THE CURRENT FLOWING
TO THE SOLENOID INSIDE THE ACTUATOR AND LETS THE HYDRAULIC PRESSURE ACTING ON EACH 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, THUS 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 IN 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
ABS ECU
A7(B), A 8(A)
(CONNECT THE ECU CONNECTOR)
(B) 6–GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION AND CHECK CONNECTOR TS–E1 NOT CONNECTED
(B)10–GROUND: APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION AND CHECK CONNECTOR TS–E1 NOT CONNECTED
(B) 1–GROUND, (A) 6–GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION, ABS WARNING LIGHT GOES OFF
(A) 8–GROUND, (A)12–GROUND: APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION, ABS WARNING LIGHT GOES OFF
(B)15–GROUND: APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION, ABS WARNING LIGHT GOES OFF
(B) 2–GROUND: ALWAYS CONTINUITY
(B)13–GROUND: ALWAYS CONTINUITY
(B)11–GROUND: APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
(B) 7–GROUND : APPROX. 12 VOLTS WITH BRAKE PEDAL DEPRESSED
(B)22–GROUND: ALWAYS APPROX. 12 VOLTS
(B)16–GROUND: APPROX. 12 VOLTS WITH ENGINE RUNNING AND PARKING BRAKE LEVER RELEASED
(DISCONNECT THE ECU CONNECTOR)
APPROX. 6 K
(B) 1 – (A) 8 :
APPROX. 6 K
(A) 6 – (A) 8 :
APPROX. 6 K
(A) 8 – (A)12:
APPROX. 0.8 – 1.3 K
(A) 7 – (A) 1 :
APPROX. 0.8 – 1.3 K
(A) 3 – (A)10 :
APPROX. 60 – 100 K
(A) 4 – (A) 5 :
APPROX. 50 – 80 K
(A) 4 – (A)11 :
(B) 3 – (B)14 : APPROX. 1.1 – 1.5 KK
(B)19 – (B)20 : APPROX. 1.1 – 1.5 KK
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