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1. Which of the following descriptions of pneumatic ABS is correct?
a.
it is an option on current trucks and trailers
b.
it is a brake-by-wire system
c.
it must have full FMVSS 121 redundancy
d.
all of the above
2. Where is a pulse wheel generator used in a truck ABS system?
a.
in the controller output circuit
b.
integral with the modulator valve
c.
wheel speed sensor assembly
d.
diagnostic display electronics
3. When some truck ABS circuits are first energized, what is the reason for the sequence of clicking noises?
a.
brakes are self-adjusting
b.
solenoids actuating during the start-up self-test
c.
service chambers actuating during the start-up self-test
d.
quick release valves actuating during the start-up self-test
b
4. When a loss of signal occurs in one wheel speed sensor on a typical truck pneumatic ABS system, which of the
following is most likely to result?
a.
ABS shuts down and reverts to normal non-ABS operation
b.
partial ABS shutdown and default to partial ABS operation
c.
ABS warning lamp illuminates to alert the driver
d.
Both B and C
d
5. How can truck ABS failure codes be displayed?
a.
LED display on the ECU
b.
blink code using a dash warning light
c.
using an EST
d.
all of the above
6. Which of the following describes what is meant by a split-coefficient stop?
a.
drive axle brakes prioritized over trailer brakes
b.
one side of a vehicle has better traction than the other under braking
c.
ABS electronic circuit brakes the axle with the most weight
d.
front wheel brake application pressure is limited
7. What electrical principle is used by a wheel speed sensor in an ABS system?
a.
three-wire voltage divider
b.
pulse generator
c.
thermistor
d.
variable capacitance sensor
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8. When the drive axle brakes of a tandem axle truck are modulated in pairs, which type of truck ABS configuration is
being referred to?
a.
4S/4M
b.
6S/4M
c.
6S/6M
d.
4S/6M
b
9. What is the current industry standard for the ABS wheel speed reluctor wheels used in highway trucks?
a.
16 tooth
b.
60 tooth
c.
100 tooth
d.
120 tooth
10. Which of the following statements regarding the illumination of a truck ABS dash light is true?
a.
illuminates briefly during self-test, then extinguishes if the self-test is successful
b.
illuminates each time the brakes are applied unless there is an ABS failure
c.
stays illuminated until a road speed of 20 mph (32 kph) is achieved
d.
flashes three times at the end of each self-test
11. When a truck ABS system is described as 6S/4M configured, how many modulator valves are used in the system?
a.
6
b.
4
c.
2
d.
1
b
12. When a tandem axle truck is equipped with a 6S/4M split configuration, how are the brakes on the drive axles
modulated during ABS braking?
a.
each wheel is modulated individually
b.
rear wheels on each side of the truck are modulated as a pair
c.
brakes on each axle are modulated as a pair
d.
brakes are modulated in a set sequence regardless of retarding velocity
b
13. When a tractor/trailer combination are both equipped with ABS brakes, how are the brakes controlled during ABS
braking?
a.
controller on the tractor masters the trailer ABS cycles
b.
tractor and trailer ABS are each managed independently by their own controllers
c.
tractor and trailers controllers network ABS braking strategy
d.
trailer controller masters the tractor ABS cycles
b
14. Which of the following could be considered ABS outputs?
a.
wheel speed sensors
b.
broadcasts over the PLC
c.
dash warning light
d.
all of the above
d
15. Depending on the generation and application of truck ABS, which pins on an ATA/SAE 7-pin trailer plug can be used
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to power-up trailer ABS units?
a.
6 and 7
b.
5 and 6
c.
4 and 7
d.
1 and 2
16. Which of the following terms have the same meaning as reluctor wheel?
a.
exciter ring
b.
chopper wheel
c.
tone wheel
d.
all of the above
17. Technician A says that an ABS wheel speed sensor generates an AC signal. Technician B says that an ABS controller
monitors the frequency of the signal it receives from the wheel speed sensor. Who is correct?
a.
Technician A only
b.
Technician B only
c.
Both A and B
d.
Neither A nor B
18. When an electronic problem causes a truck air brake system ABS shutdown, which of the following will occur?
a.
truck cannot be safely moved
b.
system reverts to normal non–ABS operation
c.
spring brakes will apply within 30 seconds
d.
driver must immediately bring the vehicle to a safe standstill
b
19. Technician A says that as the rotational speed of an ABS monitored wheel increases, the voltage generated by the
wheel speed sensor also increases. Technician B says that the frequency produced by a truck ABS wheel speed sensor
when it is at a standstill should be close to 400 Hz. Who is correct?
a.
Technician A only
b.
Technician B only
c.
Both A and B
d.
Neither A nor B
20. How many degrees of tire rotation does each tooth in a 100-tooth ABS reluctor wheel represent?
a.
360-degrees
b.
100-degrees
c.
36-degrees
d.
3.6-degrees
21. Which of the following explains why the 100-tooth reluctor wheel has become standard in truck ABS systems?
a.
insufficient voltage can be generated by 16-tooth sensors
b.
3.6-degrees of tire rotation is close to the dynamic footprint of a radial tire at 60 mph
c.
computers find it easier to monitor higher frequencies
d.
it had to be different from a tailshaft speed sensor
b
22. How many modulations per second is a typical truck pneumatic ABS capable of managing?
a.
less than one
b.
up to 3
c.
3 to 7
d.
8 to 20
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23. A current truck or trailer ABS system is required to have FMVSS 121 redundancy. What does redundancy mean in
this context?
a.
superfluous
b.
shuts down if a failure occurs
c.
ability to apply brakes immediately when a system fault is detected
d.
revert to full pneumatic circuit control in the event of ABS electronic failure
24. Technician A says that all ABS circuits are tested during a start-up self test. Technician B says that if all the
components checked during an ABS self test are verified functional, the dash ABS light remains illuminated. Who is
correct?
a.
Technician A only
b.
Technician B only
c.
Both A and B
d.
Neither A nor B
25. When an ABS brake is modulated which of the following is happening?
a.
all hold-off air is dumped
b.
all service application air is dumped
c.
hold-off air is dumped until rate of wheel deceleration normalizes
d.
service application air is cyclically dumped until rate of wheel deceleration normalizes
d
26. Technician A says that ABS modulation cycle rates are much higher in truck pneumatic brake systems than hydraulic
brake systems. Technician B says that ABS pneumatic modulation cycle rates peak at about 7 times per second. Who is
correct?
a.
Technician A only
b.
Technician B only
c.
Both A and B
d.
Neither A nor B
27. Which of the following accounts for slower modulation frequencies in truck pneumatic brake systems than equivalent
hydraulic brake systems?
a.
trucks move more slowly than automobiles
b.
compressibility of air versus that of hydraulic fluid slows switching frequency
c.
truck chassis computers function at slower clock speeds than automobile computers
d.
truck ABS system have to manage many more brakes than automobile ABS
b
28. In pneumatic ABS modulation, what happens to air diverted from the service chambers?
a.
re-routed to hold-off circuit
b.
re-routed to service reservoirs
c.
returned to supply reservoir
d.
exhausted to atmosphere
d
29. If a fail relay coil ceases to function, which of the following will result?
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a.
ABS does not function, ABS warning light does not illuminate
b.
ABS does not function, ABS warning light illuminates
c.
service brakes cannot be applied
d.
parking brakes cannot be released
b
30. Which of the following best describes how power line carrier (PLC) multiplexing takes place from a trailer to a
tractor?
a.
blue auxiliary terminal in a 7-wire trailer connector is dedicated to data bus transactions
b.
data is radio frequency (RF) superimposed over the auxiliary hardwire
c.
data is pulse width modulated (PWM) from trailer to tractor data bus
d.
data is pulse width modulated (PWM) from tractor to trailer data bus
b
31. Technician A says that when the truck brakes are applied, the more severe the braking force, the greater the role
played by the front brakes. Technician B says that it is mandatory for current trucks to include the front brakes in the ABS
loop. Who is correct?
a.
Technician A only
b.
Technician B only
c.
Both A and B
d.
Neither A nor B
32. Technician A says that in a 6S/6M highway tractor ABS, two modules are required to manage the system. Technician
B says that a 6S/6M highway tractor ABS is required for most accident avoidance electronics. Who is correct?
a.
Technician A only
b.
Technician B only
c.
Both A and B
d.
Neither A nor B
b
33. Which of the following ABS configurations is most commonly used on tandem drive highway tractors today?
a.
two-channel
b.
four-channel
c.
six-channel
d.
eight-channel
34. In a tandem drive highway tractor with a 4S/4M ABS, which axles are usually monitored and modulated?
a.
both tandem drive axles
b.
steer axle and rear drive axle
c.
steer axle and front drive axle
35. In a 4S/4M ABS, which wheels have wheel speed sensors fitted?
a.
steer axle left, steer axle right, forward drive axle right, forward drive axle left
b.
steer axle left, steer axle right, rear drive axle right, rear drive axle left
c.
steer axle left, steer axle right, forward drive axle right, rear drive axle right
d.
forward drive axle left, forward drive axle right, rear drive axle left, rear drive axle right
36. Technician A says that drive axle wheel lock under braking is a major cause of trailer jackknife. Technician B says
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that even a basic 2S/2M tractor ABS can help reduce jackknife incidents.
a.
Technician A only
b.
Technician B only
c.
Both A and B
d.
Neither A nor B
37. Which of the following ABS configurations can increase the incidence of trailer swing accidents in a semi-trailer rig?
a.
no ABS on tractor or trailer
b.
ABS on tractor, no ABS on trailer
c.
ABS on both tractor and trailer
d.
failure of PLC connection
b
38. What is the current minimum ABS requirement for a trailer brake system?
a.
2S/1M
b.
2S/2M
c.
4S/2M
d.
4S/3M
39. Technician A says that trailer ABS fault codes are stored in the controller ECU volatile memory. Technician B says
that ABS fault codes can usually be displayed at the controller ECU. Who is correct?
a.
Technician A only
b.
Technician B only
c.
Both A and B
d.
Neither A nor B
40. An ABS control ECU flashes codes that do not appear in the OEM code chart. Which of the following is the likely
cause?
a.
PLC connection to tractor is lost
b.
modulator valve assembly defective
c.
sensor circuit defective
d.
ECU defective
41. If a battery charger is used to power up a dynamic test of a trailer ABS circuit, which of the following can result?
a.
this is an appropriate way of checking trailer ABS
b.
modulator solenoid failure
c.
wheel speed sensor failure
d.
ECU failure
42. What does software such as Bendix ACom allow the technician to perform on an ABS circuit?
a.
read fault codes
b.
troubleshoot both brake and ABS failures
c.
analyze brake performance
d.
all of the above
d
43. Technician A says that as wheelbase becomes shorter in a highway truck, its resistance to yaw is reduced. Technician
B says that an ABS add-on called directional stability control uses the brake system to avoid tracking yaw. Who is
correct?
a.
Technician A only
b.
Technician B only
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c.
Both A and B
d.
Neither A nor B
44. Technician A says that when an electronic braking system (EBS) is used on an air brake system, the control circuit is
pneumatic and the actuator circuit is electronic-over-electric. Technician B says that when EBS is used at this moment in
time in North America, it is required to have full FMVSS-121 redundancy. Who is correct?
a.
Technician A only
b.
Technician B only
c.
Both A and B
d.
Neither A nor B
45. Technician A says that an advantage of EBS is that electronic signals travel through a circuit at close to the speed of
light. Technician B says that EBS response times are much faster than systems relying on pneumatics in the control
portion of a brake circuit. Who is correct?
a.
Technician A only
b.
Technician B only
c.
Both A and B
d.
Neither A nor B