ASE T4 brakes final exam questions and 100% verified
answers| grade a+.
The low air pressure indicator light and buzzer stay on with the air pressure gauges
showing 100 psi. Which of these could be the cause?
(A) A failed double check valve
(B) A leaking spring brake chamber
(C) A leaking parking brake control valve
(D) A failed low air pressure sensor
Explanation: The gauge reading of 100 psi indicates pressure well above the low-
pressure sensor threshold. As a result, options A, B, and C will not cause the light
and buzzer to stay ON. The answer is D.
Which of these could cause the tractor system air pressure to drop to zero psi after
a trailer emergency line breaks?
(A) A saturated air drier
(B) A failed tractor protection valve
(C) A brake application valve not exhausting
(D) A failed trailer service control valve
, Explanation: A failed tractor protection valve will cause air pressure in the tractor
braking system to escape after a trailer air line failure. Options A, C, and D will not
cause the tractor system air pressure to drop to zero psi. The answer is B.
After the air drier purges, the primary air pressure gauge reads 120 psi and the
secondary gauge reads 90 psi. No leaks in the system are observed. Which of these
could be the cause?
(A) A stuck-open air compressor unloader valve
(B) A failed air compressor governor
(C) A failed gauge in the instrument cluster
(D) A seized parking brake control valve
Explanation: The primary and secondary pressure gauges should read the same
pressures in a normalized state. Options A and B will affect both gauges equally.
Option D will have no effect on the system pressures. The answer is C.
A truck that has the air compressor inlet connected to the engine air cleaner
housing has excessive oil in the air brake system. This could be caused by:
(A) worn air compressor piston rings.
(B) a restricted turbocharger oil supply line.
(C) misadjusted brake chamber stroke.
(D) a leaking air control line
answers| grade a+.
The low air pressure indicator light and buzzer stay on with the air pressure gauges
showing 100 psi. Which of these could be the cause?
(A) A failed double check valve
(B) A leaking spring brake chamber
(C) A leaking parking brake control valve
(D) A failed low air pressure sensor
Explanation: The gauge reading of 100 psi indicates pressure well above the low-
pressure sensor threshold. As a result, options A, B, and C will not cause the light
and buzzer to stay ON. The answer is D.
Which of these could cause the tractor system air pressure to drop to zero psi after
a trailer emergency line breaks?
(A) A saturated air drier
(B) A failed tractor protection valve
(C) A brake application valve not exhausting
(D) A failed trailer service control valve
, Explanation: A failed tractor protection valve will cause air pressure in the tractor
braking system to escape after a trailer air line failure. Options A, C, and D will not
cause the tractor system air pressure to drop to zero psi. The answer is B.
After the air drier purges, the primary air pressure gauge reads 120 psi and the
secondary gauge reads 90 psi. No leaks in the system are observed. Which of these
could be the cause?
(A) A stuck-open air compressor unloader valve
(B) A failed air compressor governor
(C) A failed gauge in the instrument cluster
(D) A seized parking brake control valve
Explanation: The primary and secondary pressure gauges should read the same
pressures in a normalized state. Options A and B will affect both gauges equally.
Option D will have no effect on the system pressures. The answer is C.
A truck that has the air compressor inlet connected to the engine air cleaner
housing has excessive oil in the air brake system. This could be caused by:
(A) worn air compressor piston rings.
(B) a restricted turbocharger oil supply line.
(C) misadjusted brake chamber stroke.
(D) a leaking air control line
