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HET Period 4 > ABS Systems > Flashcards

ABS Systems Flashcards

1
Q

On what date did ABS become mandatory on Heavy Duty Trucks and Trailers?

A

March 1st 1998

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2
Q

What are the four main benefits of ABS systems installed on a Heavy Duty Truck or Trailer?

A

Maintains control during braking, reduces stopping distances, saves on tire flat spotting & prevents wheel lockup.

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3
Q

If you are driving a pre ABS unit, how often could you pump the brakes in the event your wheels begin to lock up?

A

Humans can pump brakes about 3 times a second.

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4
Q

How many times can an ABS controlled system actuate the brakes to control wheel lockup in an ABS event?

A

Brake corrections are performed 100 times a second.

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5
Q

When a builder is designing a tandem axle trailer, what are the minimum requirements for ABS systems installed on it?

A

Trailers require two sensors, and one modulator.

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6
Q

On a system with a three axle design, what is the most effective setup of equipment that an ABS system can have?

A

6 sensors and 6 Modulators, one for each wheel end.

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7
Q

When speaking about ABS systems, what do Channels refer to?

A

Channels refer to the number of circuits that get modulated, or the number of modulators.

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8
Q

When a tandem axle unit that is equipped with Spring Suspension, which of the two drive axles offloads first, and where are the sensors located on this setup?

A

The front axle would offload first as the springs force the weight back, so the sensors are located on this axle.

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9
Q

When a tandem axle unit that is equipped with airbag style suspension, which of the two drive axles offload first, and where are the sensors located on this setup?

A

The rear axle would offload first and as such, the sensors are located on this axle.

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10
Q

On an ABS system specced as 4S / 3M, where would the sensors and modulators be located?

A

Two sensors and Two Modulators on steer axle

Two sensors and One Modulator on the drive tandems.

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11
Q

How many teeth on average are within an ABS tone ring?

A

Between 80-120 Teeth.

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12
Q

AC Voltage signals produced by ABS Wheel Speed Sensors produce two types, what are they? How are they measured?

A

Voltage - Measured in Amplitude

Frequency - Measured in Hertz

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13
Q

If the tone ring was to move away from the sensor or vice versa, what could the resulting effects be?

A

The voltage produced inside the wheel speed sensor would reduce. This way the ECU can tell the difference between a wheel slowing, or a wheel that is coming loose or worn wheel bearings.

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14
Q

Is the Modulator Valve normally open or normally closed?

A

Normally Open - to allow free flow of air until signalled.by the ABS ECU.

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15
Q

During a normal braking event, what positions are the solenoids in, inside the Modulator valve.

A

The supply solenoid is seated and de-energized

The exhaust solenoid is unseated and de-energized

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16
Q

During an ABS event, what positions are the solenoids iin, inside the modulator valve.

A

The supply solenoid is energized in the unseated posotion

The exhaust solenoid is energized in the seated position

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17
Q

When the ABS system instructs the modulator valve to hold, what position are the solenoids in?

A

The supply solenoid is energized in the unseated position

The exhaust solenoid is de-energized in the unseated position.

18
Q

How fast are signals communicated by the ABS ECU?

A

Signals are transmitted in milliseconds.

19
Q

If you have repaired an ABS system, cleared the codes and the light remains on, what should you do?

A

Drive the vehicle in a speed between 5-10km/h to have the light go off if no faults are present.

20
Q

On which date did it become CVIP requirement to have an ABS light located on the left corner of a trailer?

A

March 1st 1998.

21
Q

On which date did it become requirement to install a trailer ABS light in the cab for operators to see.

A

March 1st 2001

22
Q

What is the one road condition that may increase the stopping distance while using ABS braking?

A

Loose dirt/gravel/sand.

23
Q

If operators change shifts, and the unit was left running. The next operator takes over and notices that the ABS light is flashing on and off, what causes this?

A

The Off-Road feature has been enabled, and was not disabled after use.

24
Q

If an operator is using a Pre-1998 trailer, and complains of the ABS light coming on during braking, what could this be?

A

The ABS system is powering up and self checking itself, as it gets its power source from the brake light pin on the trailer cord.

25
Q

Inside the new industry standard green trailer cord, what wire sizes were changed, and what were they changed to?

A

Ground is 8 gauge
Stop & Aux is 10 Gauge
Lamps are 12 Gauge

26
Q

How are fault code signals transmitted from a trailer ECU to the operator?

A

Fault code information is sent through a multiplexing link, using power line carrier or PLC technology, through the centre power pin on the trailer plug.

27
Q

When building a unit that will be equipped with Automatic Traction Control, what are the minimum numbers of Sensors and Modulators required on a Tandem axle?

A

4S 4M is the minimum but it operates better on 6S 6M

28
Q

What is the purpose behind the theory of differential braking?

A

As torque to overcome and spin causes a reduction in torque due to no traction, the braking effect raises the torque required to spin the wheel, eventually causing the other non spinning wheel to turn and drive out of the issue.

29
Q

When you are driving under 40km/h and encounter a slippery condition, what is the Traction Controls first response to the problem?

A

The traction control will begin to apply the brakes to control wheel torque and gain traction.

30
Q

When driving down the road at 60km/h and you encounter icy/slippery conditions, what will the traction controls system do to respond?

A

The traction control system will communicate with the engine ECM and de-rate the engine.

31
Q

What sorts of vehicles and trailers are best aided by an RPS system?

A

Vehicles with a high centre of gravity.

32
Q

What 4 responses can the RSC system use to slow the vehicle?

A

Reduce engine torque
Engine retarder
Apply drive axle brakes
Modulate brake pressure to trailer brakes

33
Q

What does the yaw sensor measure?

A

The yaw sensor measures rotational forces to detect jackknifing and spinouts.

34
Q

What does an accelerometer measure?

A

Lateral acceleration during cornering in order to sense rollovers.

35
Q

When a vehicle is equipped with a front axle control solenoid, what does it control?

A

The front axle control solenoid allows ATC to control the front steer axle brakes.

36
Q

If a vehicle is equipped with ABS, will it shorten the stopping distance in slippery conditions?

A

Yes

37
Q

In an air system, where is the ATC ( Traction Control) valve mounted?

A

Between the Treadle Valve and the Relay Valve.

38
Q

During an engine derate condition due to ABS/ATC, can the engine brakes provide sufficient braking to produce wheel lockup in poor road conditions?

A

Yes

39
Q

When an ABS Modulator is modulated, what is it causing within the foundation brake system?

A

Service application pressure is cycled on and off until wheel speed normalizes.

40
Q

What are the two primary functions of an ABS system?

A

Maintain control throughout braking

Reduce overall stopping distance

41
Q

What valve serves the purpose of preventing jackknifing by using differential braking?

A

The front axle control valve.

42
Q

What piece of equipment is added to the design of an air system with ESC?

A

The steering angle sensor is added.

HET Period 4 (5 decks)

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