Page 1 of 160
USPS 943 Automotive Technician EXAM
QUESTIONS AND VERIFIED ANSWERS WITH
RATIONALES JUST RELEASED
USPS 943 Automotive Technician Exam -
10 Key Exam Coverage Areas (Most Frequently Tested)
1. Engine Systems & Diagnostics - Four-stroke cycle operation, compression testing,
cylinder leakage testing, vacuum gauge readings (normal range 14-22 inHg), preignition
causes (carbon deposits), vibration damper/harmonic balancer mounted on crankshaft,
flywheel function for smoothing power impulses
2. Brake Systems - Disc brake advantages (less fade when hot), drum brake out-of-round
causing pulsating pedal, soft/spongy pedal from air in hydraulic system, maximum
allowable drum oversize (.060 inches), brake fluid moisture absorption (hygroscopic),
proportioning valve function
3. Electrical & Ignition Systems - Alternator converts AC to DC via silicon diodes, engine
timing set with strobe light/timing light, burned points indicate faulty condenser or
voltage regulator set too high, OBD-II scanner for retrieving diagnostic trouble codes
4. Fuel Systems & Carburetion - Float function closes needle valve to maintain constant
fuel level, flooding caused by stuck float needle valve, icing occurs on cool damp days,
hard starting caused by improper choke operation, black smoke indicates rich mixture,
white smoke indicates burning coolant
5. Transmission & Drivetrain - Planetary gear set component (pinion gear), two-stroke
engine produces power stroke every revolution of crankshaft, four-stroke completes
cycle in two crankshaft revolutions, PCV system common to all modern vehicles
6. Suspension & Steering - Ball joint front suspension eliminates conventional kingpin,
stabilizer bar improves cornering stability, tie rod adjustment affects toe-in, lower ball
joint is load-bearing, toe-in causes outside tire wear, toe-out causes inside tire wear
7. Emissions & Exhaust - PCV system aids prevention of air contamination, HC
(hydrocarbons) caused by misfire, NOx from high combustion temperatures, catalytic
converter restrictions indicated by gradual vacuum gauge decrease, closed crankcase
ventilation purpose
8. Diesel Engines - Fuel ignited by heat of compression (no spark plugs), gasoline cannot be
used in diesel because it ignites prematurely, glow plugs aid cold starting, diesel
combustion uses compression ignition at 400-600 psi
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9. HVAC & Cooling Systems - Radiator pressure cap increases coolant boiling point,
thermostat stuck open causes slow engine warm-up, coolant in combustion chamber
indicated by white smoke
10. Tool Usage & Shop Safety - Ammeter measures amps, ohmmeter measures ohms,
voltmeter measures volts, high-rate discharge cell tester for battery testing, Safety Data
Sheets (SDS) and OSHA compliance for shop safety
Question 1: Which of the following conditions will result when a brake drum is out of round and
the brakes are applied during normal vehicle operation on a USPS mail delivery route?
A) A low pedal that requires excessive travel before braking occurs
B) A spongy pedal that feels soft and compressible when pressed
C) A high pedal that engages the brakes too early in the travel
D) A pulsating pedal that vibrates and surges during brake application
E) A hard pedal that requires excessive force to depress
Answer: D) A pulsating pedal
Rationale: An out-of-round brake drum creates uneven contact between the brake shoes and
the drum surface during rotation . This causes the brake pedal to pulsate or vibrate when
applied, as the shoes alternately contact high and low spots on the drum, which is the most
noticeable symptom of this condition.
, Page 3 of 160
Question 2: The vibration damper, also known as a harmonic balancer, on a typical automotive
engine is securely fastened to which specific rotating engine component for proper operation?
A) The camshaft which controls valve timing and lift
B) The flywheel which stores rotational energy for smooth operation
C) The crankshaft which converts reciprocating motion to rotation
D) The oil pump drive shaft which circulates engine lubricant
E) The water pump shaft which circulates engine coolant
Answer: C) The crankshaft
Rationale: The vibration damper (harmonic balancer) is fastened to the front of the crankshaft
to absorb torsional vibrations that would otherwise cause crankshaft fatigue and failure . It is
never attached to the camshaft or transmission shafts.
Question 3: Which one of the following emission control systems is installed as standard
equipment on all cars and light trucks manufactured in the United States at the present time
according to federal regulations?
, Page 4 of 160
A) AIR - Air Injection Reaction system that pumps air into the exhaust
B) PCV - Positive Crankcase Ventilation system that recirculates blow-by gases
C) CCC - Computer Controlled Combustion system for fuel metering
D) II - Improved Ignition system for better spark control
E) ACS - Air Cleaning System for intake air filtration
Answer: B) PCV - Positive Crankcase Ventilation
Rationale: The PCV (Positive Crankcase Ventilation) system is common to all modern vehicles
and routes blow-by gases from the crankcase back into the intake manifold to be burned,
reducing hydrocarbon emissions and preventing oil contamination .
Question 4: In an automatic transmission system, which of the following components is
correctly identified as being part of a planetary gear set that provides multiple gear ratios?
A) The impeller which is part of the torque converter assembly
B) The modulator which controls shift points based on engine vacuum
C) The pinion gear which is a small gear within the planetary gear set
USPS 943 Automotive Technician EXAM
QUESTIONS AND VERIFIED ANSWERS WITH
RATIONALES JUST RELEASED
USPS 943 Automotive Technician Exam -
10 Key Exam Coverage Areas (Most Frequently Tested)
1. Engine Systems & Diagnostics - Four-stroke cycle operation, compression testing,
cylinder leakage testing, vacuum gauge readings (normal range 14-22 inHg), preignition
causes (carbon deposits), vibration damper/harmonic balancer mounted on crankshaft,
flywheel function for smoothing power impulses
2. Brake Systems - Disc brake advantages (less fade when hot), drum brake out-of-round
causing pulsating pedal, soft/spongy pedal from air in hydraulic system, maximum
allowable drum oversize (.060 inches), brake fluid moisture absorption (hygroscopic),
proportioning valve function
3. Electrical & Ignition Systems - Alternator converts AC to DC via silicon diodes, engine
timing set with strobe light/timing light, burned points indicate faulty condenser or
voltage regulator set too high, OBD-II scanner for retrieving diagnostic trouble codes
4. Fuel Systems & Carburetion - Float function closes needle valve to maintain constant
fuel level, flooding caused by stuck float needle valve, icing occurs on cool damp days,
hard starting caused by improper choke operation, black smoke indicates rich mixture,
white smoke indicates burning coolant
5. Transmission & Drivetrain - Planetary gear set component (pinion gear), two-stroke
engine produces power stroke every revolution of crankshaft, four-stroke completes
cycle in two crankshaft revolutions, PCV system common to all modern vehicles
6. Suspension & Steering - Ball joint front suspension eliminates conventional kingpin,
stabilizer bar improves cornering stability, tie rod adjustment affects toe-in, lower ball
joint is load-bearing, toe-in causes outside tire wear, toe-out causes inside tire wear
7. Emissions & Exhaust - PCV system aids prevention of air contamination, HC
(hydrocarbons) caused by misfire, NOx from high combustion temperatures, catalytic
converter restrictions indicated by gradual vacuum gauge decrease, closed crankcase
ventilation purpose
8. Diesel Engines - Fuel ignited by heat of compression (no spark plugs), gasoline cannot be
used in diesel because it ignites prematurely, glow plugs aid cold starting, diesel
combustion uses compression ignition at 400-600 psi
, Page 2 of 160
9. HVAC & Cooling Systems - Radiator pressure cap increases coolant boiling point,
thermostat stuck open causes slow engine warm-up, coolant in combustion chamber
indicated by white smoke
10. Tool Usage & Shop Safety - Ammeter measures amps, ohmmeter measures ohms,
voltmeter measures volts, high-rate discharge cell tester for battery testing, Safety Data
Sheets (SDS) and OSHA compliance for shop safety
Question 1: Which of the following conditions will result when a brake drum is out of round and
the brakes are applied during normal vehicle operation on a USPS mail delivery route?
A) A low pedal that requires excessive travel before braking occurs
B) A spongy pedal that feels soft and compressible when pressed
C) A high pedal that engages the brakes too early in the travel
D) A pulsating pedal that vibrates and surges during brake application
E) A hard pedal that requires excessive force to depress
Answer: D) A pulsating pedal
Rationale: An out-of-round brake drum creates uneven contact between the brake shoes and
the drum surface during rotation . This causes the brake pedal to pulsate or vibrate when
applied, as the shoes alternately contact high and low spots on the drum, which is the most
noticeable symptom of this condition.
, Page 3 of 160
Question 2: The vibration damper, also known as a harmonic balancer, on a typical automotive
engine is securely fastened to which specific rotating engine component for proper operation?
A) The camshaft which controls valve timing and lift
B) The flywheel which stores rotational energy for smooth operation
C) The crankshaft which converts reciprocating motion to rotation
D) The oil pump drive shaft which circulates engine lubricant
E) The water pump shaft which circulates engine coolant
Answer: C) The crankshaft
Rationale: The vibration damper (harmonic balancer) is fastened to the front of the crankshaft
to absorb torsional vibrations that would otherwise cause crankshaft fatigue and failure . It is
never attached to the camshaft or transmission shafts.
Question 3: Which one of the following emission control systems is installed as standard
equipment on all cars and light trucks manufactured in the United States at the present time
according to federal regulations?
, Page 4 of 160
A) AIR - Air Injection Reaction system that pumps air into the exhaust
B) PCV - Positive Crankcase Ventilation system that recirculates blow-by gases
C) CCC - Computer Controlled Combustion system for fuel metering
D) II - Improved Ignition system for better spark control
E) ACS - Air Cleaning System for intake air filtration
Answer: B) PCV - Positive Crankcase Ventilation
Rationale: The PCV (Positive Crankcase Ventilation) system is common to all modern vehicles
and routes blow-by gases from the crankcase back into the intake manifold to be burned,
reducing hydrocarbon emissions and preventing oil contamination .
Question 4: In an automatic transmission system, which of the following components is
correctly identified as being part of a planetary gear set that provides multiple gear ratios?
A) The impeller which is part of the torque converter assembly
B) The modulator which controls shift points based on engine vacuum
C) The pinion gear which is a small gear within the planetary gear set
