402 Auto Electricity and Electronics
Copyright by Goodheart-Willcox Co., Inc.
Figure 21-9. Diagram shows the arrangement of a typical anti-lock brake system. Note how the sensors feed data to the ECM. ECM
can then operate the hydraulic actuator when needed.
Wheel Speed
Sensor (RF)
Ignition
Switch
Battery
Fuse
Wheel Speed Sensor (LF) Wheel Speed Sensor (LR)
Fluid Pressure Circuit
Electric Circuit
Hydraulic Actuator Unit
Alternator
Motor
ABS
Warning Light
Proportioning
By-Pass Valve
Brake Light
Switch
Wheel Speed
Sensor (RR)
ABS Control Unit
or Computer
Figure 21-8. This is a variation of an ABS hydraulic actuator. It also uses a motor-driven pump to pressurize the system and solenoid-
operated valves to control pressure to each wheel brake assembly.
Motor Relay
Valve Relay
Diode
Electric
Pump Motor
Pump
Reservoir
Accumulator
Anti-Pulsation
Valve
Solenoid Valve
Check Valve