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Heavy Equipment Technician Period 4 > HET4 ABS > Flashcards

HET4 ABS Flashcards

ABS AND AIRBRAKES

1
Q

What does preventing tire skidding do for the operator?

A

Allows the operator to steer

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2
Q

Does ABS help a vehicle stay in a straight line?

A

Yes, helps avoid jacknifing a trailer

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3
Q

Describe Channels

A

the number of circuits that are modulated

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4
Q

If the governor fails is there another valve to limit air pressure on an air brake system?

A

Safety valve

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5
Q

What are some negative characteristics of nylon air brake tubing?

A

it cannot withstand high temperatures, abrasion, wear or excessive movements

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6
Q

What is the advantage of the pilot relay valve over a standard relay valve?

A

Pilot relay valve has no difference between incoming signal pressure and delivery pressure

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7
Q

In Alberta what is the minimum thickness of brake linings allowed?

A

The brake lining must be thicker than 8mm or 5/16 inch

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8
Q

When a vehicles weight is doubled, how much more power is required to stop it?

A

Double

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9
Q

True or False:

Brake lag is normal in an air brake system?

A

True

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10
Q

If a human can apply and release brakes 1-3 times per seconds, how fast does an ABS system pump the brakes?

A

up to 100 times a seconds

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11
Q

For an ABS system to perform does every wheel need t have a wheel speed sensor installed?

A

No, depends on manufacture design

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12
Q

What is needed on the wheel hub to provide ABS?

A

The tone ring/ tooth wheel/ tooth ring or exciter ring

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13
Q

What type of pulse is being generated to give a signal for the ABS system?

A

AC pulse

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14
Q

What makes up a wheel speed sensor that works with the tone ring to make up a AC pulse signal?

A

The speed sensor is a permanent magnet

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15
Q

What is voltage measured in on a vehicle with ABS?

A

Amplitude

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16
Q

How is frequency measured on an anti-lock braking system?

A

Hertz

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17
Q

Why is wheel sensor cable length important?

A

Too long it can become pinched, tangled or damaged

Too short it can stretch and break

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18
Q

What is an air ABS modulator valve is?

A

Electro-pneumatic output device

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19
Q

List some ABS terms

A 
Electronic Brake system
Vehicle dynamic control
Vehicle Stability control
Automatic traction control
Electronic stability control
roll stability control
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20
Q

Can ABS correct for operator faults or abnormal/negative conditions?

A

No

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21
Q

2S/1M translates into?

A

Two sensors/One modulator

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22
Q

Since when did ABS become mandatory on all new on-highway heavy duty trucks and trailers with air brakes?

A

March 1, 1998

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23
Q

On a three-axle configuration what system set up will provide maximum protection from flat spotting tires?

A

six sensor/six modulator (6S/6M)

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24
Q

On a tandem axle trailer, what is the minimum requirement for ABS?

A

2S/1M (two sensor/one modulator)

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25
Q

True or False

ABS used in normal braking?

A

False

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26
Q

Does suspension have any affect on braking performance?

A

Yes, worn suspension can cause poor performance from brakes

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27
Q

1 modulator makes how many brakes pulse on a tandem axle?

A

Four brakes

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28
Q

Describe Primary and Secondary axles?

A

Rear axles are considered Primary

Front/Steer axle is considered Secondary

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29
Q

True or False

It is normal for front/steer axles to have spring brakes?

A

False

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30
Q

Describe an ABS modulator as a valve?

A

Passive, Normally Open

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31
Q

As speed of tone ring increases, what else increases?

A

Voltage and frequency

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32
Q

What is the most common ABS system configuration?

A

4S/4M

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33
Q

Do wheel sensors need to be at a set clearance?

A

Yes, running clearance needs to be set.

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34
Q

Can an ECU tell the difference between the speed of a wheel and if a wheel is coming loose and moving away from the hub?

A

Yes due to voltage change vs frequency change

190402d pg 11

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35
Q

If an (AIR) ABS system has one channel, what type of system is it?

A

2S/1M also the minimum trailer requirement

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36
Q

Define the difference between Truck and Tractor?

A

Truck - self contained load, carries itself, ie. dumptruck

Tractor - pulls a load, pulls a tailer

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37
Q

On a vehicle with Air suspension, where are the wheel speed sensors usually located?

A

Usually on the REAR axle

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38
Q

On a vehicle with spring suspension/walking beam, where are the wheel speed sensors usually located?

A

Usually on the FRONT axle

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39
Q

Do lighter or heavier axles lock up wheels first?

A

The lighter the axle the more likely the wheels will lock up

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40
Q

Why do we put wheel sensors on different axles on different vehicles?

A

Depending on suspension styles, one axle will become lighter before the other axles causing it to lock up the wheels faster

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41
Q

After 1998, what is visible to the operator on the dash during start up?

A

ABS light

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42
Q

During normal operation should the ABS light be on or off?

A

During normal operation with a correctly working ABS system the light should be off

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43
Q

What type of wiring is run to wheel sensors?

A

Twisted pairs to reduce interference

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44
Q

What was required after FMVSS121 on-road vehicles?

A

Spring Brakes, Spring applied - Air released

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45
Q

What two pieces in a ABS valve package with relay valve create the brake modulation?

A

Electrically operated solenoids and Diaphragm vales

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46
Q

Chatter heard during self diagnostics of an ABS system tell a technician what?

A

Communication between electronic components

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47
Q

Where does an ECU have be to mounted for an ABS system?

A

Any location that is protected

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48
Q

True or False

ECUs are always found inside the cab of a vehicle

A

False

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49
Q

Can debris potentially affect the speed sensory/tone ring communication?

A

Yes, any metallic particles can affect the spacing of the teeth on the tone ring

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50
Q

What are the three instructions the ECU can give to the ABS valve package with relay valve?

A

Exhaust
Hold
Reapply

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51
Q

Where is the Tone ring mounted on a vehicle?

A

On the axle hub

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52
Q

What manipulates voltage being read by speed sensors?

A

Speed
Proximity
Angle

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53
Q

What information does the ECU need from the speed sensor to decide if information is within parameters?

A

Voltage and Pulse

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54
Q

Speed sensors can always be referred to as?

A

Reluctance type

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55
Q

True or False

Heavy duty and Medium duty vehicles have electric brakes?

A

FALSE

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56
Q

What type of signal is AC?

A

Analog signal, wave form/ variable

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57
Q

When one wheel slows down faster than other wheels what is it considered?

A

Wheel Skid

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58
Q

What are the 3 commands from the ECU to the electric solenoids in the ABS valves?

A

Exhaust
Hold
Reapply

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59
Q

During an ABS event operation, the ECU asks for an EXHAUST from the ABS modulator valve, what position are the solenoids in?

A

Supply solenoid is activated

Exhaust solenoid is activated

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60
Q

When the ABS modulator valve supply solenoid is energized and exhaust solenoid is de-energized what is the ECU asking from the modulator valve?

A

To HOLD

holding position

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61
Q

When the ABS modulator is preparing to return to normal brake application supply state what are the electric solenoids states?

A

Both exhaust and supply solenoid are de-energized

62
Q

How quickly does an ECU receive and transmit signals?

A

Milliseconds

63
Q

What are considered off-board diagnostics?

A

Scan tool or PC

64
Q

What is considered on-board diagnostics?

A

Blink code switch or warning lamp

65
Q

True or False

The ABS modulator valve sends signals to the ECU?

A

False, only receives

66
Q

How many wires run to the modulator?

A

Three wires, using a common ground

67
Q

During normal operation of the vehicle what are the ABS modulator solenoids doing?

A

Nothing, de-energized

68
Q

On a trailer where is ECU possibly mounted?

A

On the air reservoir with a relay valve

69
Q

When arc welding what can prevent damaging the ECU?

A

Unplugging or disconnecting ECU

70
Q

Why is the ABS lamp position important?

A

Due to ABS being apart of driving laws, it needs to be in view of the transport officers
If it is an in the cab warning light, the vehicle operator must be able to see the light

71
Q

Vehicles with ABS prefer to run tires with circumferences that are within what difference of each other? (inchs)

A

3/4 inch max differences

72
Q

What is the purpose of ABS?

A

To stop tire skid/wheel lock up

73
Q

With the new green-jacketed trailer cord, and increased wire size, what was the change in voltage drops?

A

Eliminates voltage drops

74
Q

PIN/WIRE 7 used to be auxiliary power, what has it become in new equipment with ABS?

A

ECU. ABS diagnostics from trailer to tractor

75
Q

PLC stands for?

A

Power Line Carrier

76
Q

PRE 1998 7-PIN has what J code?

A

J560

77
Q

After March 1998 what J code is used for the 7-PIN connector?

A

J1939

78
Q

In an off-road situation, why would ABS be unwanted for decrease braking distance?

A

Off-Roads that are loose build up in the front wheels when wheels are locked acting as a wedge decreases stopping times

79
Q

How many bits in a bite?

A

8 bits in a bite

80
Q

How many wires are used to communicate ABS?

A

Two wires, redundant system

81
Q

True or False:

You must have ABS but Automatic traction control is optional? (Heavy Equipment not automotive application)

A

TRUE

82
Q

What are the two ways ATC reduces wheel spin?

A
  1. Braking a specific wheel -differential braking

2. Reduces the amount of torque delivered to the drive wheels

83
Q

Locking a differential can give what?

A

Traction

84
Q

Below 40km/h what type of braking does ATC use when needed?

A

Differential braking

85
Q

Above 40km/h what is done to combat wheel spin with ATC?

A

Torque reduction

86
Q

If differential braking is done above 40km/h what can occur?

A

Shock loading the driveline and high foundation brake temperatures

87
Q

How is torque reduction communicated through the vehicle?

A

Datalink J-1939 between ABS ECU and engine ECU

88
Q

What are some precautions when working on vehicles with electronics?

A
  • Disconnect the battery/ECU before welding
  • Do not disconnect any electrical component with the system powered
  • Use only high impedance meters for voltage testing
  • Never probe conductor insulation
  • Keep excessive heat away from electronic components
89
Q

If the ATC light is blinking does that mean the ATC is currently activated?

A

No, the blinking light means the system has been disabled by the operator

90
Q

Torque reduction is used on what type of engines?

A

Electronically controlled

91
Q

Is an ATC valve an input or output device from the ECU?

A

Output device

92
Q

What should be released before working on, testing or disabling an ABS system?

A

Release system air pressure and/or hydraulic brake pressure

93
Q

What must be done before using a vehicle with ATC on a dynamometer?

A

The ATC system must be disabled

94
Q

What are three common ways to disable the ATC system for a dyno test?

A

Pressing on the blink code switch for at least three seconds
Removing ABS circuit breaker/fuse
Using a scan tool/PC

95
Q

RSC stands for?

A

Roll stability control

96
Q

What systems does the RSC work with to limit the possibility of a rollover condition?

A

ABS/ATC

97
Q

What inputs does the ECU of the RSC system need to make decisions?

A

Wheel Speed Sensors

Lateral/side to side movement - plots lateral acceleration limit (accelerometer)

98
Q

What does the RSC system use to slow the vehicle?

A

Reduces engine torque
Engage engine/driveline retarders
Apply brake pressure to the drive axle brakes (from ATC valve)
Modulate brake pressure to the trailer brakes

99
Q

Which wheels receive the most braking force, to avoid a roll over?

A

The wheels that bear the heavier loads

100
Q

What must be done to take an RSC system to an ESC system?

A

Add components - ESC module
Front axle control valve
Steering angle sensor (SAS)
Brake demand pressure sensor

101
Q

What conditions can an ESC system prevent?

A

Jackknife or drift-out condition

102
Q

ESC stands for?

A

Electronic stability control

103
Q

An advanced ECU that monitor many different functions uses what SAE J systems?

A

J1708/J1587, can communicate with tractor J560

104
Q

The SAS gets its input from?

A

The operator

105
Q

SAS stands for?

A

Steering angle sensor

106
Q

What is inside the ESC module to understand conditions?

A

Yaw Sensor and Accelerometer

107
Q

The Yaw sensor inside the ESC module measures what?

A

Rotational forces - detects jackknifing/spin out

108
Q

The accelerometer inside the ESC module measures what?

A

Lateral acceleration during cornering

109
Q

What does the ESC module communicate with?

A

ABS ECU

110
Q

What should be done when troubleshooting air ABS issues?

A
  1. Talk to the operator
  2. Check basic service brake system
  3. Visually inspect ABS components
  4. Operate the vehicle confirm problem and test ABS system operation
  5. Contact the equipment manufacturer’s tech support
111
Q

What is the easiest way to confirm warning lamp/indicators work?

A

When the key is first turned to on, all lamps should illuminate

112
Q

What is the normal resistance reading from a wheel speed sensor to the ECU?

A

500 - 2000 ohms

113
Q

What can excessive wheel bearing end play result in?

A

erratic wheel speed sensor readings

114
Q

How are the exhaust and supply solenoids tested on an ABS modulator control valve assembly?

A

With power disconnected, check the resistance of the solenoid from ground terminal to circuit terminal.
12V system - 4-8 ohms
24V system 8-16 ohms
make sure to clean contacts before testing
pg 21 190402e

115
Q

Americans follow FMVSS 121 what is the Canadian counter part?

A

CMVSS 121

116
Q

Channels refers to?

A

Modulators

117
Q

What types of road conditions does the RSC work in?

A

Dry, good road conditions

118
Q

What type of road conditions does the ESC system work in?

A

Wet/Slippery Road conditions

119
Q

True or False:

If there is a fault in the ABS system the foundation brakes will not work?

A

False

120
Q

Where is the ATC valve located in the air circuit of the truck?

A

Between the treadle valve (primary) and service brake relay

121
Q

Before removing wheels what should be checked for play?

A

The wheel bearing adjustment, end play

122
Q

Before removing air lines what should be done to the system?

A

Air system should be drained

123
Q

What is the purpose of dielectric grease when using it on electrical connections?

A

To help prevent moisture from entering the cavity during normal operation

124
Q

True or False:

ABS on a hydraulic brake system can correct for operator faults?

A

False

125
Q

Why is DOT 5 brake fluid not recommended for brake systems with ABS?

A

The fluid does not absorb moisture and retains tiny air bubbles

126
Q

If there is damage in the ABS modulator valve, can it affect normal hydraulic brake action?

A

Yes, I.e. Internal valve is jammed closed

190402f pg 15

127
Q

How many solenoid valves are needed for each wheel location?

A

One inlet and one outlet

128
Q

What is the best way to repair an ABS harness?

A

Manufactures recommendation or replace

129
Q

When mounting a hydro-boost power brake what needs to be inspected?

A

An air gap/pedal play

To avoid Brake Drag

130
Q

Metering Valve purpose is?

A

Brake Timing, apply rear brakes first

131
Q

Proportioning valve does what to a disc and drum hydraulic brake system?

A

Blocks the line to the drum since they self energized

132
Q

What suspension component can affect braking ability?

A

Worn/broken shock absorber

133
Q

What is the operators complaint when the brake fluid is low?

A

Spongy brakes, air is now in the system

134
Q

Where is the ATC valve is located?

A

Between the brake treadle valve and service brake relay at the REAR drive axle(s)

135
Q

How is an ECU grounded?

A

Through a dedicated ground

136
Q

In a normal braking event what is the ABS modulator valve doing?

A

Nothing, both solenoids are de-energized and allows air to flow through supply port to delivery port

137
Q

In an ABS event operation what is the valve doing with both solenoids energized?

A

Air coming in the supply port cannot exhaust or go through delivery port, and air from delivery side can exhaust

138
Q

When the ABS valve is HOLDING what is happening inside the valve?

A

Supply air is trapped inside the valve and the delivery side cannot exhaust

139
Q

Where is the ABS modulator valve located on the system?

A

Between relay valve and brake chamber (pot)

140
Q

What type of wires are used in the ABS system?

A

Twisted Pairs

Shielded wires

141
Q

True or False:

All ABS components are serviceable?

A

FALSE

142
Q

When bleeding a hydraulic brake system with ABS, is there most likely a pattern to follow?

A

Yes

143
Q

What is the general range of waveforms from speed sensors/tone rings?

A

0-400Hz

144
Q

What can a tone ring be safely heated to before installing?

A

121°C (250°F) in boiling water or over

145
Q

What does water in brake fluid cause?

A

Lower Boiling point

146
Q

What could give you a false diagnosis of an ECU you believe was faulty?

A

Aftermarket radio transmission devices installed on the vehicle - if too close to ECU or ABS control module

147
Q

What causes brake fade?

A

Excessive heat

148
Q

After servicing a wheel hub on a vehicle with ABS what will need to be done?

A

Reset the speed sensor depth

149
Q

Does an engine exhaust brake, ie. tier 3, have enough braking power to cause a wheel lock up?

A

Yes, some ABS systems will auto turn off engine brakes

150
Q

What is the best way to test an ECU?

A

using a break out box

151
Q

In an ABS system what uses pulse generator principle?

A

Wheel speed sensor

152
Q

When does an ABS ECU only monitor wheel speeds?

A

During a non-skiding brake application

Heavy Equipment Technician Period 4 (13 decks)

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