ASE Short Answer 3 — Questions and Answers
Question 1: What is the purpose of the PCV (Positive Crankcase Ventilation) valve?
- Route crankcase blow-by gases back to the intake to be burned (Correct answer)
- Regulate fuel pressure
- Control transmission shift points
- Cool the exhaust manifold
Correct answer: Route crankcase blow-by gases back to the intake to be burned
The PCV valve meters blow-by vapors from the crankcase into the intake so they are reburned instead of vented.
Question 2: A technician finds milky, light-brown oil on the dipstick. What does this most likely indicate?
- Coolant mixing with the engine oil (Correct answer)
- Normal oil aeration
- Excessive fuel dilution
- Worn timing chain
Correct answer: Coolant mixing with the engine oil
A milky appearance means coolant has entered the oil, often from a blown head gasket or cracked component.
Question 3: Which type of transmission uses a torque converter instead of a clutch to transfer engine power?
- Automatic transmission (Correct answer)
- Manual transmission
- Sequential gearbox
- Dual dry-clutch manual
Correct answer: Automatic transmission
An automatic transmission uses a fluid-coupling torque converter rather than a driver-operated clutch.
Question 4: What is the recommended first step before working on any high-voltage hybrid or electric vehicle system?
- Disable and isolate the high-voltage system per the service procedure (Correct answer)
- Disconnect the 12-volt battery only
- Drain the cooling system
- Remove the wheels
Correct answer: Disable and isolate the high-voltage system per the service procedure
High-voltage systems must be properly de-energized and isolated using the manufacturer's procedure before service.
Question 5: A customer reports a steering wheel shimmy felt mainly at highway speed. What is the most common cause?
- Out-of-balance front tire/wheel assembly (Correct answer)
- Low brake fluid
- Worn spark plugs
- Clogged cabin air filter
Correct answer: Out-of-balance front tire/wheel assembly
Speed-related steering shimmy is most commonly caused by an unbalanced front wheel assembly.
Question 6: In the OBD-II system, what does a P0420 code generally indicate?
- Catalyst system efficiency below threshold (Bank 1) (Correct answer)
- Misfire on cylinder 4
- Evaporative system large leak
- Mass airflow circuit high input
Correct answer: Catalyst system efficiency below threshold (Bank 1)
P0420 means the catalytic converter on Bank 1 is operating below its efficiency threshold.
Question 7: What tool is used to accurately measure the thickness of a brake rotor to determine if it can be resurfaced?
- Micrometer (Correct answer)
- Test light
- Feeler gauge
- Torque wrench
Correct answer: Micrometer
A micrometer measures rotor thickness so it can be compared against the discard specification.
ASE Short Answer 3
What is the purpose of the PCV (Positive Crankcase Ventilation) valve?