Yamaha YP250A 1999 Supplementary Service Manual page 40

ANTI-LOCK BRAKE SYSTEM (ABS)
Power
Voltage
regulator
Front brake
Front brake
switch
switch signal
circuit
Rear brake
Rear brake
switch
switch signal
circuit
Stop lamp
Brake
signal
light circuit
Starter
Starter
switch
switch
signal
circuit
Starter switch
Front
wheel sensor
Digital
Rear
conversion
wheel sensor
circuit
Electronic control unit (ECU)
Electronic control unit 1 controls the ABS and is
installed inside the taillight unit. To protect from
water invasion, it is enveloped by a cover 2 .
As shown in the block diagram below, the ECU
takes in the wheel sensor signals from front and
rear wheels and also receives the signals from
various monitor circuits. Two of main and sub mi-
crocomputers are installed in the ECU providing
mutual monitoring.
Electronic control unit (ECU)
Memory
Main CPU
(Main microcomputer)
Sub CPU
(Sub microcomputer)
32
CHAS
Motor monitor
circuit
Solenoid
Solenoid valve
motor
Hydraulic
unit (HU)
Solenoid drive
circuit
Fail-safe relay Solenoid
drive circuit
Motor relay
drive circuit
Warning light
ABS warning light
drive circuit
Operation mode
switching circuit
Checker
Fault code
output circuit
Front wheel speed
Speedometer
output circuit
Motor
Fail-safe
Motor relay
relay