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USPS Exam 943: Section 2 — Automotive Technician Practice Question
Bank (2026–2027) Comprehensive Practice Bank — Section 2: Automotive
Technician (30 Minutes)
Advanced Diagnostics, Computerized Engine Controls,
Electronic Systems, Emissions, HVAC, and Complex Repair
Procedures
Official Exam Structure: Section 2 (Automotive Technician) is a
30-minute timed section that tests advanced diagnostic and
repair knowledge. It is taken in conjunction with Section 1
(Automotive Mechanic, 60 minutes). The combined exam is
used for Automotive Technician and Lead Automotive Mechanic
positions.
SECTION 1: ADVANCED ENGINE PERFORMANCE &
DIAGNOSTICS
Question 1. During a cylinder leakage test, air is heard escaping
through the tailpipe while the tested cylinder is pressurized.
Which condition should the technician suspect?
A) Worn piston rings
B) A leaking exhaust valve
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C) A defective head gasket
D) A worn intake valve
Correct Answer: B) A leaking exhaust valve
Rationale: Air escaping through the tailpipe during a cylinder
leakage test indicates that compressed air is passing through
the exhaust valve and into the exhaust system. This is a classic
sign of a leaking or burnt exhaust valve. Worn piston rings
would allow air into the crankcase (heard through the oil filler),
and a head gasket leak would typically allow air into the cooling
system or between adjacent cylinders.
Question 2. A technician performs a cylinder leakage test and
observes air bubbles in the radiator. What is the most likely
cause?
A) Worn piston rings
B) A defective head gasket or cracked cylinder head
C) A leaking intake valve
D) A restricted exhaust system
Correct Answer: B) A defective head gasket or cracked cylinder
head
Rationale: Air bubbles in the radiator during a cylinder leakage
test indicate that compressed air is entering the cooling system
through a breach in the head gasket or a crack in the cylinder
head. This is a definitive diagnostic indicator for combustion
chamber-to-coolant passage leaks.
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Question 3. During a running compression test, a technician
observes that the compression reading is significantly lower
than the cranking compression reading. What does this
indicate?
A) Worn piston rings
B) A restricted intake or exhaust system
C) A leaking head gasket
D) Normal engine operation
Correct Answer: B) A restricted intake or exhaust system
Rationale: Running compression that is significantly lower than
cranking compression indicates a restriction in the intake or
exhaust system that limits airflow into or out of the cylinder
during engine operation.
Question 4. A vacuum gauge reading fluctuates rapidly between
10" and 22" at idle. What is the most likely cause?
A) Worn valve guides
B) A vacuum leak
C) Worn valve springs or a sticking valve
D) A restricted exhaust system
Correct Answer: C) Worn valve springs or a sticking valve
Rationale: A rapidly fluctuating vacuum gauge reading
indicates uneven cylinder filling, commonly caused by worn
valve springs or a sticking valve. A steady low reading indicates
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worn rings or a vacuum leak, while a gradually declining
reading indicates an exhaust restriction.
Question 5. A vehicle has a P0300 (random misfire) DTC. Which
of the following should the technician check FIRST?
A) Replace all spark plugs
B) Check for vacuum leaks and fuel pressure
C) Replace the ignition coils
D) Replace the catalytic converter
Correct Answer: B) Check for vacuum leaks and fuel pressure
Rationale: A P0300 (random misfire) indicates misfires across
multiple cylinders, which is typically caused by a systemic issue
such as a vacuum leak, low fuel pressure, or a faulty sensor. The
technician should first check for common causes before
replacing components.
Question 6. A vehicle has a P0301 DTC (misfire cylinder 1).
What is the most efficient diagnostic approach?
A) Replace the spark plug and ignition coil in cylinder 1
B) Swap the ignition coil from cylinder 1 to cylinder 2 and see if
the misfire moves
C) Replace all fuel injectors
D) Replace the engine control module
Correct Answer: B) Swap the ignition coil from cylinder 1 to
cylinder 2 and see if the misfire moves
Rationale: When a single-cylinder misfire code is present,
USPS Exam 943: Section 2 — Automotive Technician Practice Question
Bank (2026–2027) Comprehensive Practice Bank — Section 2: Automotive
Technician (30 Minutes)
Advanced Diagnostics, Computerized Engine Controls,
Electronic Systems, Emissions, HVAC, and Complex Repair
Procedures
Official Exam Structure: Section 2 (Automotive Technician) is a
30-minute timed section that tests advanced diagnostic and
repair knowledge. It is taken in conjunction with Section 1
(Automotive Mechanic, 60 minutes). The combined exam is
used for Automotive Technician and Lead Automotive Mechanic
positions.
SECTION 1: ADVANCED ENGINE PERFORMANCE &
DIAGNOSTICS
Question 1. During a cylinder leakage test, air is heard escaping
through the tailpipe while the tested cylinder is pressurized.
Which condition should the technician suspect?
A) Worn piston rings
B) A leaking exhaust valve
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C) A defective head gasket
D) A worn intake valve
Correct Answer: B) A leaking exhaust valve
Rationale: Air escaping through the tailpipe during a cylinder
leakage test indicates that compressed air is passing through
the exhaust valve and into the exhaust system. This is a classic
sign of a leaking or burnt exhaust valve. Worn piston rings
would allow air into the crankcase (heard through the oil filler),
and a head gasket leak would typically allow air into the cooling
system or between adjacent cylinders.
Question 2. A technician performs a cylinder leakage test and
observes air bubbles in the radiator. What is the most likely
cause?
A) Worn piston rings
B) A defective head gasket or cracked cylinder head
C) A leaking intake valve
D) A restricted exhaust system
Correct Answer: B) A defective head gasket or cracked cylinder
head
Rationale: Air bubbles in the radiator during a cylinder leakage
test indicate that compressed air is entering the cooling system
through a breach in the head gasket or a crack in the cylinder
head. This is a definitive diagnostic indicator for combustion
chamber-to-coolant passage leaks.
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Question 3. During a running compression test, a technician
observes that the compression reading is significantly lower
than the cranking compression reading. What does this
indicate?
A) Worn piston rings
B) A restricted intake or exhaust system
C) A leaking head gasket
D) Normal engine operation
Correct Answer: B) A restricted intake or exhaust system
Rationale: Running compression that is significantly lower than
cranking compression indicates a restriction in the intake or
exhaust system that limits airflow into or out of the cylinder
during engine operation.
Question 4. A vacuum gauge reading fluctuates rapidly between
10" and 22" at idle. What is the most likely cause?
A) Worn valve guides
B) A vacuum leak
C) Worn valve springs or a sticking valve
D) A restricted exhaust system
Correct Answer: C) Worn valve springs or a sticking valve
Rationale: A rapidly fluctuating vacuum gauge reading
indicates uneven cylinder filling, commonly caused by worn
valve springs or a sticking valve. A steady low reading indicates
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worn rings or a vacuum leak, while a gradually declining
reading indicates an exhaust restriction.
Question 5. A vehicle has a P0300 (random misfire) DTC. Which
of the following should the technician check FIRST?
A) Replace all spark plugs
B) Check for vacuum leaks and fuel pressure
C) Replace the ignition coils
D) Replace the catalytic converter
Correct Answer: B) Check for vacuum leaks and fuel pressure
Rationale: A P0300 (random misfire) indicates misfires across
multiple cylinders, which is typically caused by a systemic issue
such as a vacuum leak, low fuel pressure, or a faulty sensor. The
technician should first check for common causes before
replacing components.
Question 6. A vehicle has a P0301 DTC (misfire cylinder 1).
What is the most efficient diagnostic approach?
A) Replace the spark plug and ignition coil in cylinder 1
B) Swap the ignition coil from cylinder 1 to cylinder 2 and see if
the misfire moves
C) Replace all fuel injectors
D) Replace the engine control module
Correct Answer: B) Swap the ignition coil from cylinder 1 to
cylinder 2 and see if the misfire moves
Rationale: When a single-cylinder misfire code is present,
