Auto 1

1. Chapter Nine
Brake Anti-lock Brake System
(ABS) Theory
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2. Objectives
 Discuss purpose and operation of antilock
brake systems
 Explain basic operation of traction control
systems
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3. Antilock Brake Systems (ABS)
 Speed Sensors
 Monitor wheel speed to control ABS application
 Sensors can be either AC signal generators or Hall-
Effect type aka: Magnetic Resonance Element
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4. Antilock Brake Systems (ABS)
 Speed Sensors
 Vehicles can have:
 one speed sensor= one channel ABS
 three speed sensors=three channel ABS
 four speed sensors=four channel ABS
 Sensors usually match the number of channels
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5. Antilock Brake Systems (ABS)
 Pressure Controllers-Hydraulic Control Unit
 Control pressure regulation
 Commanded by ABS controller
 Number of channels designate number of solenoids
that can isolate different brake components
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6. Antilock Brake Systems (ABS)
 Pressure Controllers-Hydraulic Control Unit
 Solenoids can only hold pressure, or release pressure
 Can’t increase pressure
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7. Antilock Brake Systems (ABS)
 ABS Operation
 When brake pedal is depressed, controller monitors
each channel for brake lockup
 If lockup is noted, controller activates solenoids to
bring vehicle under control
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8. Antilock Brake Systems (ABS)
 ABS Operation
 Defect detected
 System turns on a warning lamp and stores a code
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10. Traction Control Systems
 Method of transferring power from a spinning drive
wheel to a wheel with more traction
 Two types of traction control
 Brake control only
 Brake and throttle/engine timing control
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11. Summary
 ABS and traction control can provide a
safer operating environment
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