ASE Practice Test #1 3 — Questions and Answers
Question 1: A vehicle has a cooling system that loses coolant with no visible external leaks. What should the technician check FIRST?
- Replace the radiator cap
- Perform a block test (combustion leak test) to check for exhaust gases in the coolant, and a pressure test to find internal leaks at the head gasket or EGR cooler (Correct answer)
- Drain and refill the cooling system
- Replace the water pump
Correct answer: Perform a block test (combustion leak test) to check for exhaust gases in the coolant, and a pressure test to find internal leaks at the head gasket or EGR cooler
Coolant loss without visible external leaks suggests an internal leak — the coolant is being consumed into the combustion chamber or entering another system. A block test (chemical test kit placed over the coolant filler) detects combustion gases in the coolant, confirming a head gasket or cylinder crack. A cooling system pressure test while monitoring for drops can also reveal a slow leak. White exhaust smoke and sweet-smelling exhaust are additional symptoms of internal coolant consumption.
Question 2: What does a "High Resistance" result in a voltage drop test on a ground circuit indicate?
- The component is drawing too much current
- There is unwanted resistance (from corrosion, loose connection, or damaged wire) in the ground path, reducing current flow and causing the component to malfunction (Correct answer)
- The battery voltage is too high
- The ground circuit is functioning normally
Correct answer: There is unwanted resistance (from corrosion, loose connection, or damaged wire) in the ground path, reducing current flow and causing the component to malfunction
A voltage drop test measures resistance in a circuit by measuring the voltage consumed by the circuit while current flows. A properly functioning ground should show less than 0.1–0.2V drop (very low resistance). Excessive voltage drop (e.g., 0.5V or more) on a ground indicates corrosion, a loose connection, or damaged wire is impeding current flow. The component receives less current, causing dim lights, slow motors, or electrical malfunctions. The test identifies resistance location without disconnecting the circuit.
Question 3: When performing a 4-wheel alignment, the technician measures the rear axle thrust angle. What does a non-zero thrust angle indicate?
- The rear toe adjustment is perfectly aligned to the vehicle centerline
- The rear axle is not perpendicular to the vehicle's centerline — the vehicle will "dog track" (rear tires do not follow the path of the front tires) (Correct answer)
- The front wheels need camber adjustment
- The steering wheel is off-center only
Correct answer: The rear axle is not perpendicular to the vehicle's centerline — the vehicle will "dog track" (rear tires do not follow the path of the front tires)
The thrust angle is the angle of the rear axle's direction relative to the vehicle's geometric centerline. If the thrust angle is not zero, the rear axle is angled to one side, pushing the rear of the vehicle sideways ("dog tracking"). On a vehicle with non-adjustable rear suspension, the front wheels must be aligned to the thrust angle (thrust line alignment) rather than the vehicle centerline, to prevent steering wheel off-center and tire wear. Adjustable rear suspension can correct the thrust angle directly.
Question 4: What is the purpose of the EVAP system purge valve in a fuel evaporative emission control system?
- To allow fuel vapors stored in the charcoal canister to be purged into the engine intake for combustion when conditions allow (Correct answer)
- To vent excess pressure from the fuel tank to atmosphere
- To seal the charcoal canister from the atmosphere when the engine is running
- To recirculate exhaust gas back into the intake manifold
Correct answer: To allow fuel vapors stored in the charcoal canister to be purged into the engine intake for combustion when conditions allow
The EVAP system captures fuel vapors from the fuel tank and routes them to a charcoal canister for storage. The purge valve, commanded by the ECM, opens under appropriate conditions (engine warm, load present) to flow stored vapors from the canister into the intake manifold where they mix with the air-fuel charge and are burned. This prevents vapors from venting to atmosphere. The ECM adjusts fuel trims to compensate for the additional fuel from canister purging.
Question 5: A customer complains their vehicle pulls to the right while braking. What is the MOST likely cause?
- Right front tire overinflated
- A stuck or seized left front brake caliper piston not applying, or a collapsed brake hose on the left side restricting brake fluid flow to the left front caliper (Correct answer)
- Low brake fluid level in the reservoir
- Worn rear brake shoes equally on both sides
Correct answer: A stuck or seized left front brake caliper piston not applying, or a collapsed brake hose on the left side restricting brake fluid flow to the left front caliper
Brake pull occurs when braking force is unequal between the two sides. If the left front brake is not applying or applying less effectively than the right, more braking force is applied on the right side, pulling the vehicle right. A seized caliper piston that does not extend, a collapsed flexible brake hose that restricts hydraulic pressure, or contaminated brake linings on one side are the most common causes. The vehicle pulls toward the side with MORE braking force (the right side in this case).
Question 6: Which scan tool data parameter BEST indicates throttle body deposits are causing idle quality issues?
- Long-term fuel trim (LTFT) significantly positive at idle, indicating the ECM is adding fuel to compensate for less air than expected through the partially restricted throttle bore (Correct answer)
- Negative long-term fuel trim at cruise speed
- Coolant temperature above normal
- Battery voltage below 12V
Correct answer: Long-term fuel trim (LTFT) significantly positive at idle, indicating the ECM is adding fuel to compensate for less air than expected through the partially restricted throttle bore
Throttle body carbon deposits reduce airflow through the throttle bore, especially at idle (small throttle opening). The MAF sensor or MAP sensor detects less air than expected, and the ECM compensates by adding fuel to maintain stoichiometry — resulting in a positive (additive) long-term fuel trim at idle. Cleaning the throttle body typically improves idle quality and returns fuel trims toward zero. If fuel trims are significantly positive only at idle and normal at cruise, throttle body restriction is a likely cause.
ASE Practice Test #1 3
A vehicle has a cooling system that loses coolant with no visible external leaks.
What should the technician check FIRST?