ASVAB Automotive Information Test 5 — Questions and Answers
Question 1: What is the purpose of VANOS or variable valve timing (VVT) systems?
- Control fuel injector pulse width
- Optimize valve opening and closing timing across different RPM ranges (Correct answer)
- Regulate oil pressure at idle
- Advance ignition spark timing only
Correct answer: Optimize valve opening and closing timing across different RPM ranges
Variable valve timing systems adjust when intake and/or exhaust valves open and close based on engine speed and load, improving power, efficiency, and emissions across the RPM range.
Question 2: A technician notices a milky, frothy substance on the oil dipstick. What does this most likely indicate?
- The oil is overdue for a change
- Coolant is mixing with the engine oil (Correct answer)
- The oil filter is clogged
- The PCV valve is stuck open
Correct answer: Coolant is mixing with the engine oil
A milky or frothy appearance on the dipstick indicates coolant contamination of the engine oil, typically caused by a blown head gasket or cracked engine block.
Question 3: What is the purpose of a vehicle's traction control system (TCS)?
- Keep the vehicle level on hills
- Prevent drive wheels from spinning excessively during acceleration (Correct answer)
- Distribute braking force front to rear
- Lock the differential during cornering
Correct answer: Prevent drive wheels from spinning excessively during acceleration
Traction control detects when a drive wheel spins faster than the others during acceleration and reduces engine power or applies the brake to that wheel to restore grip.
Question 4: What does a vehicle's knock sensor detect?
- Exhaust system leaks
- Abnormal combustion (detonation/pinging) in the cylinders (Correct answer)
- Oil pressure drops
- Camshaft timing errors
Correct answer: Abnormal combustion (detonation/pinging) in the cylinders
The knock sensor detects the vibration frequencies produced by engine knock (pre-ignition/detonation) and signals the ECU to retard ignition timing to prevent engine damage.
Question 5: Which of the following best describes the role of the torque converter's stator?
- Connect the engine to the transmission input shaft directly
- Redirect fluid from the turbine back to the pump to multiply torque (Correct answer)
- Prevent the converter from overheating
- Lock the pump and turbine together at highway speeds
Correct answer: Redirect fluid from the turbine back to the pump to multiply torque
The stator sits between the pump and turbine and redirects returning fluid in a direction that assists the pump rotation, multiplying torque output at low vehicle speeds.
Question 6: When replacing brake pads, why is it necessary to compress the caliper piston back into its bore?
- To bleed air from the brake line
- To create clearance for the thicker new brake pads to fit over the rotor (Correct answer)
- To test the caliper for leaks
- To reset the ABS sensor
Correct answer: To create clearance for the thicker new brake pads to fit over the rotor
As brake pads wear, the caliper piston extends outward; new pads are thicker, so the piston must be pushed back in to allow the caliper assembly to fit over the rotor.
Question 7: What is the primary function of an engine's harmonic balancer (crankshaft damper)?
- Drive the water pump and alternator
- Reduce torsional vibrations in the crankshaft (Correct answer)
- Time the ignition system
- Support the front main bearing
Correct answer: Reduce torsional vibrations in the crankshaft
The harmonic balancer absorbs and dampens the torsional (twisting) vibrations created by combustion pulses acting on the crankshaft, preventing fatigue cracks and bearing wear.
ASVAB Automotive Information Test 5
What is the purpose of VANOS or variable valve timing (VVT) systems?