Automotive TechnologyAutomotive Technology

Chapter ObjectivesChapter Objectives• Explain how antilock brake systems work Explain how antilock brake systems work

to bring a vehicle to a controlled stop.to bring a vehicle to a controlled stop.• Describe the differences between an Describe the differences between an

integrated and a nonintegrated ABS.integrated and a nonintegrated ABS.• Briefly describe the major components of a Briefly describe the major components of a

two-wheel antilock brake system.two-wheel antilock brake system.• Briefly describe the major components of a Briefly describe the major components of a

four-wheel antilock brake system.four-wheel antilock brake system.

• Describe the operation of the major Describe the operation of the major components of an antilock brake system.components of an antilock brake system.

• Describe the operation of the major Describe the operation of the major components of automatic traction and components of automatic traction and stability control systems.stability control systems.

• Explain the best procedure for finding Explain the best procedure for finding ABS faults.ABS faults.

• List the precautions that should be List the precautions that should be followed whenever working on an ABS.followed whenever working on an ABS.

First introduced on 1954 LincolnFirst introduced on 1954 Lincoln 1978 Mercedes made first ABS that 1978 Mercedes made first ABS that

worked wellworked well Can’t defy the law of nature or Can’t defy the law of nature or

physicsphysics Reduces distance to stopReduces distance to stop Most effective on dry concreteMost effective on dry concrete

Antilock BrakesAntilock Brakes

Normal driving will not notice differenceNormal driving will not notice difference Anti-lock EventAnti-lock Event Unrestricted tire rotation is 0% slipUnrestricted tire rotation is 0% slip Tire locked up is 100% slipTire locked up is 100% slip When we have 100% slip, the tire loses When we have 100% slip, the tire loses

traction and vehicle motion changes into traction and vehicle motion changes into heat energy. (not very effective!)heat energy. (not very effective!)

Maximum Braking ForceMaximum Braking Force Between 10 and 20 Percent Slip Between 10 and 20 Percent Slip

WET CONCRETEWET CONCRETE

Locked wheels Locked wheels prevent directional prevent directional controlcontrol

Wheel lock up can Wheel lock up can be prevented by be prevented by limiting brake limiting brake pressure to a point pressure to a point just short of lockup.just short of lockup.

• Pressure ModulationPressure Modulation• Pedal FeelPedal Feel

Diagonally Split SystemDiagonally Split System• Controls Two Hydraulic circuits (2 channel)Controls Two Hydraulic circuits (2 channel)

Front/Rear Split SystemFront/Rear Split System• Controls Three Hydraulic circuit (3 channel)Controls Three Hydraulic circuit (3 channel)

Full Four Wheel SystemFull Four Wheel System• Controls Four Hydraulic Circuits (4 channel) Controls Four Hydraulic Circuits (4 channel)

(page 203) Usually intergrated with traction (page 203) Usually intergrated with traction controlcontrol

Page 228CPage 228C

Normal operation when in conventional Normal operation when in conventional mode (if warning light, disables ABS)mode (if warning light, disables ABS)

Heavy braking causes hydraulic pressure Heavy braking causes hydraulic pressure modulation (Pedal Feel)modulation (Pedal Feel)

Integrated System (Combined parts)227CIntegrated System (Combined parts)227C Non-Integrated System (Separate Parts)Non-Integrated System (Separate Parts) ABS operates independently of base ABS operates independently of base

systemsystemABS Operation/Modes Description - Page 226C - 227CABS Operation/Modes Description - Page 226C - 227C

ELECTRONIC CONTROL ELECTRONIC CONTROL UNITUNIT

Inputs and Outputs Inputs and Outputs (228C)(228C)

Some ABS ECU’s have Some ABS ECU’s have dual boardsdual boards

Controls HCUControls HCU Full DiagnosticsFull Diagnostics Controls Warning LightsControls Warning Lights Can control each wheel Can control each wheel

brake independently. brake independently. (four channel) Most are (four channel) Most are three channelthree channel

Mechanical NoisesMechanical Noises

HYDRAULIC CONTROL UNIT HYDRAULIC CONTROL UNIT (HCU)(HCU)

PagePage261C261C

TevesTevesMk IVMk IV

Hydraulic Control UnitHydraulic Control Unit(Integral)(Integral)

Hydraulic Control UnitHydraulic Control Unit(Non-Integral)(Non-Integral)

ACCUMULATORACCUMULATOR

Stores high Stores high pressure brake pressure brake fluid from Pumpfluid from Pump

Supplies high Supplies high pressure fluid in pressure fluid in ABS mode ABS mode

2800 to 3400 PSI2800 to 3400 PSI

Must bleed beforeMust bleed beforereplacement or replacement or serviceservice

257C257C

PUMP AND MOTORPUMP AND MOTOR

Motor is 12V Electric (235C)Motor is 12V Electric (235C) Works independently of the base Works independently of the base

brake systembrake system Pressurizes brake fluid up to 2800 Pressurizes brake fluid up to 2800

psi.psi. Turns on when ever pressure drops Turns on when ever pressure drops

below a predetermined levelbelow a predetermined level Some are replaceable seperatelySome are replaceable seperately

WHEEL SPEED SENSORSWHEEL SPEED SENSORS

Detects rotation of Detects rotation of wheelwheel

Permanent magnet Permanent magnet typetype

3 Parts 3 Parts • Permanent magnetPermanent magnet• CoilCoil• YokeYoke

Induces AC voltage Induces AC voltage varied frequencyvaried frequency

229C to 231C229C to 231C

RELUCTOR (Tone Ring)RELUCTOR (Tone Ring)

ELECTRICAL ELECTRICAL COMPONENTSCOMPONENTS

HCU SOLENOID RELAYHCU SOLENOID RELAY• Used on some systemsUsed on some systems

HCU MOTOR RELAYHCU MOTOR RELAY MAIN POWER RELAY MAIN POWER RELAY PRESSURE SWITCHES (430L)PRESSURE SWITCHES (430L)• Generally will turn on Anti-lock Warning Generally will turn on Anti-lock Warning

lightlight

Pg 235CPg 235C

PUMP MOTOR RELAYPUMP MOTOR RELAY

B+B+

Cruise ControlCruise ControlTCCTCC

Brake LightsBrake LightsCHMSLCHMSLABSABS

Switch OperationSwitch OperationOrOrPower RelayPower Relay

SELF DIAGNOSTICSSELF DIAGNOSTICS

Each time Ignition Each time Ignition is turned on ABS is turned on ABS does a self does a self diagnostic check.diagnostic check.

Some systems do Some systems do check while car is check while car is moving.moving.

Indicator Lamp Indicator Lamp Operation Operation

ABS ABS ComponentsComponents• Hydraulic Hydraulic

ComponentsComponents– AccumulatorAccumulator– Valve BlockValve Block

– Booster pumpBooster pump– Booster/master cylinder assemblyBooster/master cylinder assembly

AccumulatorAccumulator

Other Hydraulic ComponentsOther Hydraulic Components– Fluid accumulatorsFluid accumulators– Hydraulic control unitHydraulic control unit–Main valveMain valve–Modulator unitModulator unit– Solenoid valveSolenoid valve– Valve block assemblyValve block assembly–Wheel circuit valvesWheel circuit valves

Electrical/Electronic ComponentsElectrical/Electronic Components– ABS control moduleABS control module– Brake pedal sensorBrake pedal sensor– Data link connector (DLC)Data link connector (DLC)– Diagnostic trouble code (DTC)Diagnostic trouble code (DTC)– Indicator lightsIndicator lights– Lateral acceleration sensorLateral acceleration sensor– Pressure switchPressure switch– Pressure differential switchPressure differential switch– RelaysRelays– Wheel speed sensorWheel speed sensor– Toothed ringToothed ring

• Four-Wheel Systems (Integral)Four-Wheel Systems (Integral)

ABS System – No BrakingABS System – No Braking

• Four-Wheel Systems (Integral)Four-Wheel Systems (Integral)

ABS System – ABS in OperationABS System – ABS in Operation

• GM ABS-VIGM ABS-VI• Add on SystemAdd on System• ElectromagneticElectromagnetic• Fast acting solenoid Fast acting solenoid

valvesvalves• Screw PlungersScrew Plungers• 4 Channel4 Channel• Can cycle 7 times per Can cycle 7 times per

secondsecond• 5 Separate 5 Separate

Diagnostic modes Diagnostic modes

• General Motors' General Motors' Electromagnetic Electromagnetic Antilock Brake Antilock Brake SystemsSystems

• Automatic Automatic Traction Traction ControlControl

• Integration Integration with Traction with Traction ControlControl

Automatic Stability ControlAutomatic Stability Control

Automatic Stability ControlAutomatic Stability Control

Automatic Stability ControlAutomatic Stability Control

Antilock Brake System ServiceAntilock Brake System Service• Safety PrecautionsSafety Precautions• Relieving Accumulator PressureRelieving Accumulator Pressure

Diagnosis and TestingDiagnosis and Testing• Pre-Diagnostic InspectionPre-Diagnostic Inspection• Visual InspectionVisual Inspection• Test DriveTest Drive• Self-DiagnosisSelf-Diagnosis• Testers and Scanning ToolsTesters and Scanning Tools• Testing Components with ABS Scan ToolsTesting Components with ABS Scan Tools

• Testing Components with a Lab ScopeTesting Components with a Lab Scope

• Testing Components with a Lab ScopeTesting Components with a Lab Scope

• Component ReplacementComponent Replacement–Wheel speed sensor serviceWheel speed sensor service– Brake system bleedingBrake system bleeding