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, RIGHT REAR WHEEL AND 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 IS DEPRESSED. (3) PARKING BRAKE SW SIGNAL A SIGNAL IS INPUT TO TERMINAL PKB OF THE ABS ECU WHEN THE PARKING BRAKE LEVER IS PULLED UP. (4) DECELERATION SENSOR SIGNAL LATERAL ACCELERATION IS DETECTED AND INPUT TO THE ABS ECU. 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 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 A 6(A), A 7(B) ABS ACTUATOR (A) 1–GROUND : ALWAYS CONTINUOUS (B) 1, (B) 3, (B) 4, (B) 6–GROUND : APPROX. 1.20 (IGNITION SW OFF) (B) 2–(A) 4: 4–6 (IGNITION SW OFF) A10, A11, A31, A32 ABS SPEED SENSOR FRONT LH, RH, REAR LH, RH 1–2: 0.8–1.3 K (20˚C, 68˚F) A18 (B), A19(A) ABS ECU (A)12–GROUND : 10–14 VOLTS WITH IGNITION SW ON (A) 2, (A)15–GROUND: ALWAYS CONTINUOUS (A)25–GROUND : ALWAYS 10–14 VOLTS (A)1, (A)13, (A)14,(A)26,–GROUND: 10–14 VOLTS WITH IGNITION SW ON (B)14–GROUND : CONTINUITY WITH PARKING BRAKE LEVEL PULLED UP (B) 6–GROUND :10–14 VOLTS WITH STOP LIGHT SW ON (BRAKE PEDAL DEPRESSED) P 5 PARKING BRAKE SW 1–GROUND: CLOSED WITH PARKING BRAKE LEVER PULLED UP S11 STOP LIGHT SW 1–2: CLOSED WITH BRAKE PEDAL DEPRESSED 162