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HET4 > 402D: Air Antilock Brake Systems > Flashcards

402D: Air Antilock Brake Systems Flashcards

1
Q

Will conventional braking continue if a portion of the ABS system fails?

A

Yes

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2
Q

What is the basic purpose of ABS?

A

Monitors wheel speeds and modulates brake application to:
- Maintain control of vehicle
- Reduce stopping distance
- Reduce tire flat spotting

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3
Q

How fast can ABS modulate brake application to each wheel?

A

Up to 100 times per second

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4
Q

Can an ABS system provide extra braking force?

A

No

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5
Q

When did ABS become mandatory on all on-highway heavy duty trucks and trailers equipped with air brakes?

A

March 1, 1998

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6
Q

To eliminate the need for extra components while still providing adequate braking, on what axle would the ABS wheel speed sensors be located in a tandem axle assembly with spring suspension?

A

Front axle

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7
Q

To eliminate the need for extra components while still providing adequate braking, on what axle would the ABS wheel speed sensors be located in a tandem axle assembly with air suspension?

A

Rear axle

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8
Q

What type of ABS system is the minimum requirement on a trailer?

A

2S/1M

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9
Q

What type of ABS system would provide the maximum protection from flat spotting due to tire skidding on a three axle configuration?

A

6S/6M

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10
Q

What is the common ABS configuration on a tandem axle tractor?

A

4S/4M

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11
Q

What do channels refer to in an ABS system?

A

The number of modulators

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12
Q

What is the purpose of the tone ring in an ABS system?

A

Works with the wheel speed sensor to generate an AC signal corresponing to wheel speed.

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13
Q

How many teeth does a tone ring typically have?

A

80 to 120

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14
Q

What is a wheel speed sensor?

A

A permanent magnet wrapped in fine copper wire that generates the AC signal corresponding to the wheel speed

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15
Q

What allows the speed sensor to be held in place and adjusted?

A

Spring clip

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16
Q

What are the two components to an AC signal?

A

Voltage - Will decrease as gap between sensor and tone ring increases
Freequency - Measured in hertz. Will increase with increased wheel speed

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17
Q

How is the distance between the tone ring and speed sensor set?

A

Push the speed sensor until the face of the sensor contacts the tone ring . Once the wheel rotates, the sensor will slide back slightly and have the proper running clearance.

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18
Q

Where in the air brake system is the air brake modulator valve located?

A

Drive Axles: Between the relay valve and air brake chamber

Steer Axle: Between the quick release valve and brake chamber

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19
Q

What are the three stages of an ABS modulator valve as it modulates air brake application pressure?

A

Exhaust
Hold
Reapply

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20
Q

During a normal brake application, what position are the ABS modulator valves in?

A

Supply Solenoid: De-energized
Exhaust Solenoid: De-energized

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21
Q

During the first stage of an ABS event, what position are the ABS modulator valves in?

A

Stage: Exhaust

Supply Solenoid: Energized
Exhaust Solenoid: Energized

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22
Q

During the second stage of an ABS event, what position are the ABS modulator valves in?

A

Stage: Holding

Supply Solenoid: Energized
Exhaust Solenoid: De-energized

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23
Q

During the final stage of an ABS event, what position are the ABS modulator valves in?

A

Stage: Reapply

Supply Solenoid: De-energized
Exhaust Solenoid: De-energized

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24
Q

On trucks, motor coaches, and commercial buses, when did the ABS light on the dash become mandatory?

A

March 1, 2001

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25
Q

Where is the ABS indicator/warning light located on trailers built after March 1, 1998?

A

Left rear corner, facing outward

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26
Q

What is the minimum ABS configuration a truck must have before it can be equipped with a traction control valve?

A

4S/4M

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27
Q

As of March 1, 1998, the trailer antilock ECU receives its power through what pin in the trailer connector?

A

Auxillary/centre pin

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28
Q

What are two methods that an ATC system can use to reduce the amount of wheel spin on slippery roads?

A

At speeds less than 40km/h
- Differential Braking
- Torque Reduction

At speeds greater than 40km/h
- Torque Reduction only

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29
Q

Durring a wheel spin condition on a vehicle equiped with ATC and differential braking, how does the ECU control the transfer of torque from the spinning wheel to the stationary wheel?

A
  • ATC valve sends air the service relay valve
  • ABS modulator valve blocks the air on the side with the stationary wheel
  • ABS modulator valve applies enough braking pressure to the spinning wheel to slow it down, which also transfers torque through the differential to the other wheel

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30
Q

Where in the air brake system is the ATC valve located?

A

Between the treadle valve and service brake relay valve

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31
Q

What are the three airline connections into an ATC valve?

A
  • Treadle valve
  • Service relay valve
  • Primary air tank

And an electrical connection to the ECU

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32
Q

What is an advantage of the deep snow and mud option in a ATC system?

A

Allows the wheels to spin slightly faster to throw off mud and snow caught in the tire treads

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33
Q

Why is it important to disconnect the ATC system when testing a vehicle on a chassis dynamometer?

A

The ATC will try to control the wheel spin and you wont be able to obtain a true torque and horsepower reading

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34
Q

Where is the RSC (Roll Stability Control) valve located?

A

In the secondary air system between the treadle valve and the tractor protection valve

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35
Q

What system helps provide protection to a tractor or tractor trailer combo from loss of stability and rollover?

A

Roll Stability Control (RSC)
- Monitors wheel speed sensors and lateral acceleration

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36
Q

What responses can the RSC valve do to prevent a rollover?

A

. Reduce engine torque
. Engage engine /driveline retarders
. Apply brake pressure to the drive axle brakes
. Modulate brake pressure to the trailer brakes

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37
Q

What sensors do ESC modules use to prevent a jackknife or spinout?

A
  • Yaw sensor
  • Accelerometer (to mesaure lateral acceleration)

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38
Q

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

A

Safety valve

HET4 (44 decks)

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