ASE T4 BRAKES
Comprehensive Resource To Help You Ace 2026-2027
Exams Includes Frequently Tested Questions With
ELABORATED 100% Correct COMPLETE SOLUTIONS
Guaranteed Pass First Attempt!! Current Update!!
1. Which of the following could set an antilock braking system (ABS) wheel
speed sensor code:
A. Faulty modulator hold solenoid
B. Faulty modulator release solenoid
C. Incorrect wheel bearing adjustment
D. Incorrect brake adjustment - Correct Answer: Answer A is
incorrect. A faulty solenoid would not cause a wheel speed sensor
code. It could cause a modulator valve code.
Answer B is incorrect. A faulty solenoid would not cause a wheel speed
sensor code. It could cause a modulator valve code
Answer C is correct. A loose wheel bearing adjustment can cause a faulty
wheel speed sensor and a wheel speed sensor code.
Answer D is incorrect. An incorrect brake adjustment may cause a dragging
brake but would not cause a wheel speed sensor code
2. The air drier purged too often. Technician A says the air drier delivery check
valve may be leaking. Technician B says a leaking wet tank could be the
cause. Who is correct?
A. A only
B. B only
C. Both A and B
D. Neither A nor B - Correct Answer: Answer A is incorrect.
Technician B is also correct.
, Answer B is incorrect. Technician A is also correct.
Answer C is correct. A leaking air drier check valve will allow the wet tank to
drain back through the air drier. This will cause air pressure to drop to
governor cut-in rapidly. The air compressor will again build tank pressure
and unload, and the sequence will start over. A leaking wet tank will cause
the air pressure to fall rapidly and the compressor to build air again and
then cut out. This too will cause the air drier to purge often.
Answer D is incorrect. Both technicians are correct.
3. The safety valve releases on the air tank. Which of the following is the most
likely cause?
A. Plugged line from the supply tank to the governor
B. Faulty tractor protection valve
C. Stuck spitter on the air drier
D. Faulty secondary tank - Correct Answer: Answer A is correct. If
the line from the supply tank to the governor were plugged the
governor would not unload the compressor.
Answer B is incorrect. The tractor protection valve could not cause
excessive pressure.
Answer C is incorrect. A stuck spitter would prevent the air drier from
purging.
Answer D is incorrect. A faulty secondary tank could leak, but that would
not cause excessive air pressure.
4. A truck with hydraulic disc/drum brakes has a high firm pedal with poor
stopping. Which of the following could be the cause?
A. The brakes are adjusted too loose.
B. The brake linings are glazed.
C. The brake pedal pushrod is too long.
D. The driveline parking brake is misadjusted. - Correct Answer:
Answer A is incorrect. If drum brakes are adjusted too loose the pedal
, will be low because the pedal will need to travel farther to take up
the clearance.
Answer B is correct. Glazed brake linings will not create the friction needed
to stop the truck but will allow the pedal to feel high and firm.
Answer C is incorrect. A pushrod that is too long would cause the brakes to
drag.
Answer D is incorrect. The driveline parking brake adjustment would not
cause a low pedal. It is not connected to the service brakes.
5. Air pressure builds up on a truck in 1.5 minutes. The specification manual
says it should take 3.5 minutes. Technician A says the air tanks could have
water buildup. Technician B says the air tanks could have oil buildup. Who is
correct?
A. A only
B. Bonly
C. Both A and B
D. Neither A nor B - Correct Answer: Answer A is incorrect. Both
technicians are correct.
Answer B is incorrect. Both technicians are correct.
Answer C is correct. Oil or water buildup will reduce the volume and result
in a decreased air buildup time.
Answer D is incorrect. Both technicians are correct.
6. Brake fluid is leaking from the rear of a master cylinder on a truck equipped
with hydro-boost brakes. Which of the following is the most likely cause?
A. By-passing master cylinder
B. Primary seal leaking
C. Secondary seal leaking
D. Brake booster leaking - Correct Answer: Answer A is incorrect. A
by-passing master cylinder does not create an external leak; it creates
a low pedal.
, Answer B is correct. A primary seal leaking would create a leak here.
Answer C is incorrect. A secondary seal leak causes an internal leak Answer
D is incorrect. A brake booster does not leak brake fluid.
7. Air pressure buildup time on a truck equipped with a gear-driven air
compressor is greater than specification. Which of the following is the most
likely cause?
A. A slipping drive
B. A leaking service relay valve
C. A leaking primary air tank
D. A leaking parking brake chamber - Correct Answer: Answer A is
incorrect. A gear-driven compressor drive may knock, but it does not
usually slip. It either works or it does not turn the compressor at all.
Answer B is incorrect. The service relay valve is not activated during the air
pressure buildup test.
Answer C is correct. A leaking primary air tank will cause extended air
pressure build time.
Answer D is incorrect. The parking brakes do not have air during the
compressor build time test.
8. Air leaks from the left-front modulator valve during a service brake
application. There are no ABS codes. Which of the following could be the
cause?
A. Service relay
B. Parking brake relay
C. Modulator valve
D. Brake chamber - Correct Answer: Answer A is incorrect. The
service relay will not cause air to leak from the modulator valve.
Answer B is incorrect. The parking brake relay will not cause the modulator
valve to leak.
Comprehensive Resource To Help You Ace 2026-2027
Exams Includes Frequently Tested Questions With
ELABORATED 100% Correct COMPLETE SOLUTIONS
Guaranteed Pass First Attempt!! Current Update!!
1. Which of the following could set an antilock braking system (ABS) wheel
speed sensor code:
A. Faulty modulator hold solenoid
B. Faulty modulator release solenoid
C. Incorrect wheel bearing adjustment
D. Incorrect brake adjustment - Correct Answer: Answer A is
incorrect. A faulty solenoid would not cause a wheel speed sensor
code. It could cause a modulator valve code.
Answer B is incorrect. A faulty solenoid would not cause a wheel speed
sensor code. It could cause a modulator valve code
Answer C is correct. A loose wheel bearing adjustment can cause a faulty
wheel speed sensor and a wheel speed sensor code.
Answer D is incorrect. An incorrect brake adjustment may cause a dragging
brake but would not cause a wheel speed sensor code
2. The air drier purged too often. Technician A says the air drier delivery check
valve may be leaking. Technician B says a leaking wet tank could be the
cause. Who is correct?
A. A only
B. B only
C. Both A and B
D. Neither A nor B - Correct Answer: Answer A is incorrect.
Technician B is also correct.
, Answer B is incorrect. Technician A is also correct.
Answer C is correct. A leaking air drier check valve will allow the wet tank to
drain back through the air drier. This will cause air pressure to drop to
governor cut-in rapidly. The air compressor will again build tank pressure
and unload, and the sequence will start over. A leaking wet tank will cause
the air pressure to fall rapidly and the compressor to build air again and
then cut out. This too will cause the air drier to purge often.
Answer D is incorrect. Both technicians are correct.
3. The safety valve releases on the air tank. Which of the following is the most
likely cause?
A. Plugged line from the supply tank to the governor
B. Faulty tractor protection valve
C. Stuck spitter on the air drier
D. Faulty secondary tank - Correct Answer: Answer A is correct. If
the line from the supply tank to the governor were plugged the
governor would not unload the compressor.
Answer B is incorrect. The tractor protection valve could not cause
excessive pressure.
Answer C is incorrect. A stuck spitter would prevent the air drier from
purging.
Answer D is incorrect. A faulty secondary tank could leak, but that would
not cause excessive air pressure.
4. A truck with hydraulic disc/drum brakes has a high firm pedal with poor
stopping. Which of the following could be the cause?
A. The brakes are adjusted too loose.
B. The brake linings are glazed.
C. The brake pedal pushrod is too long.
D. The driveline parking brake is misadjusted. - Correct Answer:
Answer A is incorrect. If drum brakes are adjusted too loose the pedal
, will be low because the pedal will need to travel farther to take up
the clearance.
Answer B is correct. Glazed brake linings will not create the friction needed
to stop the truck but will allow the pedal to feel high and firm.
Answer C is incorrect. A pushrod that is too long would cause the brakes to
drag.
Answer D is incorrect. The driveline parking brake adjustment would not
cause a low pedal. It is not connected to the service brakes.
5. Air pressure builds up on a truck in 1.5 minutes. The specification manual
says it should take 3.5 minutes. Technician A says the air tanks could have
water buildup. Technician B says the air tanks could have oil buildup. Who is
correct?
A. A only
B. Bonly
C. Both A and B
D. Neither A nor B - Correct Answer: Answer A is incorrect. Both
technicians are correct.
Answer B is incorrect. Both technicians are correct.
Answer C is correct. Oil or water buildup will reduce the volume and result
in a decreased air buildup time.
Answer D is incorrect. Both technicians are correct.
6. Brake fluid is leaking from the rear of a master cylinder on a truck equipped
with hydro-boost brakes. Which of the following is the most likely cause?
A. By-passing master cylinder
B. Primary seal leaking
C. Secondary seal leaking
D. Brake booster leaking - Correct Answer: Answer A is incorrect. A
by-passing master cylinder does not create an external leak; it creates
a low pedal.
, Answer B is correct. A primary seal leaking would create a leak here.
Answer C is incorrect. A secondary seal leak causes an internal leak Answer
D is incorrect. A brake booster does not leak brake fluid.
7. Air pressure buildup time on a truck equipped with a gear-driven air
compressor is greater than specification. Which of the following is the most
likely cause?
A. A slipping drive
B. A leaking service relay valve
C. A leaking primary air tank
D. A leaking parking brake chamber - Correct Answer: Answer A is
incorrect. A gear-driven compressor drive may knock, but it does not
usually slip. It either works or it does not turn the compressor at all.
Answer B is incorrect. The service relay valve is not activated during the air
pressure buildup test.
Answer C is correct. A leaking primary air tank will cause extended air
pressure build time.
Answer D is incorrect. The parking brakes do not have air during the
compressor build time test.
8. Air leaks from the left-front modulator valve during a service brake
application. There are no ABS codes. Which of the following could be the
cause?
A. Service relay
B. Parking brake relay
C. Modulator valve
D. Brake chamber - Correct Answer: Answer A is incorrect. The
service relay will not cause air to leak from the modulator valve.
Answer B is incorrect. The parking brake relay will not cause the modulator
valve to leak.
