TRANSIT BUS ASE TEST EXAM LATEST 2026 UPDATED QUESTIONS AND
VERIFIED 100% SOLUTIONS (2026/2027) |A+ GRADED |GUARANTEED
PASS
A bus is diagnosed with an active modulator valve code. A technician first should:
A. check for parts availability before putting the bus out of service.
B. clear codes and road test.
C. clean contacts and check specified solenoid resistance.
D. check continuity between modulator valve and the ECU. - Answers -Answer C is correct. You
must first verify if the modulator valve solenoids are defective. Cleaning the solenoid contacts
and "ohm out" the solenoids is the right diagnostic procedure. If the modulator solenoids are
found to be in good condition, checking continuity between the modulator valve and ECU is the
next diagnostic step; therefore, Answer D is wrong. Answer A is wrong. You must verify a faulty
valve before part replacement. Answer B is wrong. You cannot
clear an active code/fault.
The parking brakes will not hold when yard tested on a bus. Which of the following should be
done FIRST?
A. Pull the wheels and replace the brake linings.
B. Replace the bus spring brake control valve.
C. Test the bus air supply pressure.
D. Check bus slack adjuster free stroke dimensions. - Answers -Answer D is correct. When the
parking brake fails to hold during yard testing, the first thing to check is the slack adjuster free
stroke; remember that parking brake effectiveness depends entirely on brake adjustment.
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,A bus equipped with air brakes completely loses the primary air reservoir. Under these
conditions, how is the relay section of a dual-circuit, air brake foot valve actuated?
A. Air pressure from the secondary reservoir
B. Air pressure from the primary section of the foot valve
C. Mechanically, by direct foot pressure
D. Mechanically, by the primary piston - Answers -Answer D is correct. The relay piston is
actuated mechanically by the primary piston in the event of loss of primary
circuit air. The foot pedal acts on the primary piston which drives it down until it contacts the
relay piston to actuate the
secondary circuit.
The discharge valve in an air compressor:
A. directs air into the primary tank.
B. prevents compressed air in the discharge line from returning to the compressor cylinder.
C. prevents the pressure in the compressor cylinder from becoming too high.
D. allows compressed air to pass into the governor. - Answers -Answer B is correct. The
discharge valve in a typical air compressor is a one-way check valve that permits compressed air
to exit the cylinder, but closes when cylinder pressure is less than pressure from the other side
of the discharge valve.
During a brake inspection, a technician tests the air supply system and finds that buildup is slow.
Which of these is the Most-Likely cause?
A. Clogged compressor inlet filter
B. Leak in a spring brake chamber
C. Air leak in the secondary service line
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, D. Restriction in the governor line - Answers -Answer A is correct. A restricted air inlet will
increase air pressure buildup time.
Answer B is wrong. The spring brake chamber is only charged with air when the parking brakes
are released. Answer C is wrong. The secondary service line is only charged with air when the
service brakes are applied. Answer D is wrong. A restricted governor line will only affect
governor operation.
All of the following are part of an air compressor EXCEPT:
A. piston rings.
B. the crankshaft.
C. the discharge valve.
D. the governor. - Answers -Answer D is correct. An air compressor has pistons, a crankshaft,
and a discharge valve. The governor is always a separate component that may be mounted on
the compressor or remotely.
When diagnosing a sensor fault. Technician A says, first check the wiring harness and verify
good continuity. Technician B says a defective wheel bearing adjustment on the drive axle could
put on the ABS fault light. Who is right?
A. A only
B. B only
C. Both A and B
D. Neither A nor B - Answers -Answer B is correct. A defective bearing adjustment can contact
the sensor and increase the sensor/tone wheel gap.
Technician A is incorrect because the first step in diagnosing a sensor fault would be to check
the specified sensor resistance with an ohmmeter. The next would be to check the sensor AC
voltage output by rotating the wheel. A reading of.2 volts AC at 30 rpm would verify a good
output signal.
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VERIFIED 100% SOLUTIONS (2026/2027) |A+ GRADED |GUARANTEED
PASS
A bus is diagnosed with an active modulator valve code. A technician first should:
A. check for parts availability before putting the bus out of service.
B. clear codes and road test.
C. clean contacts and check specified solenoid resistance.
D. check continuity between modulator valve and the ECU. - Answers -Answer C is correct. You
must first verify if the modulator valve solenoids are defective. Cleaning the solenoid contacts
and "ohm out" the solenoids is the right diagnostic procedure. If the modulator solenoids are
found to be in good condition, checking continuity between the modulator valve and ECU is the
next diagnostic step; therefore, Answer D is wrong. Answer A is wrong. You must verify a faulty
valve before part replacement. Answer B is wrong. You cannot
clear an active code/fault.
The parking brakes will not hold when yard tested on a bus. Which of the following should be
done FIRST?
A. Pull the wheels and replace the brake linings.
B. Replace the bus spring brake control valve.
C. Test the bus air supply pressure.
D. Check bus slack adjuster free stroke dimensions. - Answers -Answer D is correct. When the
parking brake fails to hold during yard testing, the first thing to check is the slack adjuster free
stroke; remember that parking brake effectiveness depends entirely on brake adjustment.
1|Page
,A bus equipped with air brakes completely loses the primary air reservoir. Under these
conditions, how is the relay section of a dual-circuit, air brake foot valve actuated?
A. Air pressure from the secondary reservoir
B. Air pressure from the primary section of the foot valve
C. Mechanically, by direct foot pressure
D. Mechanically, by the primary piston - Answers -Answer D is correct. The relay piston is
actuated mechanically by the primary piston in the event of loss of primary
circuit air. The foot pedal acts on the primary piston which drives it down until it contacts the
relay piston to actuate the
secondary circuit.
The discharge valve in an air compressor:
A. directs air into the primary tank.
B. prevents compressed air in the discharge line from returning to the compressor cylinder.
C. prevents the pressure in the compressor cylinder from becoming too high.
D. allows compressed air to pass into the governor. - Answers -Answer B is correct. The
discharge valve in a typical air compressor is a one-way check valve that permits compressed air
to exit the cylinder, but closes when cylinder pressure is less than pressure from the other side
of the discharge valve.
During a brake inspection, a technician tests the air supply system and finds that buildup is slow.
Which of these is the Most-Likely cause?
A. Clogged compressor inlet filter
B. Leak in a spring brake chamber
C. Air leak in the secondary service line
2|Page
, D. Restriction in the governor line - Answers -Answer A is correct. A restricted air inlet will
increase air pressure buildup time.
Answer B is wrong. The spring brake chamber is only charged with air when the parking brakes
are released. Answer C is wrong. The secondary service line is only charged with air when the
service brakes are applied. Answer D is wrong. A restricted governor line will only affect
governor operation.
All of the following are part of an air compressor EXCEPT:
A. piston rings.
B. the crankshaft.
C. the discharge valve.
D. the governor. - Answers -Answer D is correct. An air compressor has pistons, a crankshaft,
and a discharge valve. The governor is always a separate component that may be mounted on
the compressor or remotely.
When diagnosing a sensor fault. Technician A says, first check the wiring harness and verify
good continuity. Technician B says a defective wheel bearing adjustment on the drive axle could
put on the ABS fault light. Who is right?
A. A only
B. B only
C. Both A and B
D. Neither A nor B - Answers -Answer B is correct. A defective bearing adjustment can contact
the sensor and increase the sensor/tone wheel gap.
Technician A is incorrect because the first step in diagnosing a sensor fault would be to check
the specified sensor resistance with an ohmmeter. The next would be to check the sensor AC
voltage output by rotating the wheel. A reading of.2 volts AC at 30 rpm would verify a good
output signal.
3|Page
