Question: Which of the following is an appropriate description of the engine valve lift?

Choices:

• A. The larger the valve lift, the more the intake air volume decreases
• B. The larger the cam base circle diameter, the smaller the lift
• C. If the lift is excessive, valve spring surging is more likely to occur
• D. ✅ The variable valve lift mechanism changes the lift according to the operating conditions

Explanation:

The variable valve lift mechanism changes the valve lift according to the engine's operating conditions (RPM and load) to optimize charging efficiency. By making the lift small in the low RPM range and large in the high RPM range, performance is improved.

Question: Which of the following is inappropriate as a description of the engine cylinder head gasket?

Choices:

• A. The gasket maintains airtightness and liquid-tightness between the cylinder head and the cylinder block
• B. If the tightening torque of the gasket is insufficient, leaks of coolant or combustion gas will occur
• C. ✅ Metal gaskets have lower heat resistance than asbestos gaskets
• D. Reusing a gasket should be avoided as it can cause leaks

Explanation:

Metal gaskets are made of metal and therefore have higher heat resistance than asbestos gaskets, allowing them to withstand high temperatures and pressures. In modern engines, metal gaskets are primarily used.

Question: Which of the following is an appropriate description of the engine intake port shape?

Choices:

• A. The larger the port cross-sectional area, the more the low-speed torque improves
• B. ✅ Helical ports generate a vertical vortex (tumble flow) in the intake air
• C. The port shape does not affect the charging efficiency
• D. Straight ports have high intake resistance

Explanation:

Helical ports generate a vertical vortex (tumble flow) in the intake air through a spiral-shaped passage, promoting turbulence of the air-fuel mixture in the combustion chamber and improving the combustion speed. This enhances combustion efficiency.

Question: Which of the following is inappropriate as a description of the mechanical efficiency of a 4-cycle engine?

Choices:

• A. Mechanical efficiency is the value obtained by dividing the brake power by the indicated power
• B. The greater the friction loss, the lower the mechanical efficiency
• C. Accessory drive losses affect mechanical efficiency
• D. ✅ Mechanical efficiency never exceeds 100%

Explanation:

Mechanical efficiency is the value of the net power (shaft output) divided by the indicated power (theoretical output generated in the cylinder) and is always 1.0 (100%) or less. Mechanical efficiency decreases due to friction loss and accessory drive loss.

Question: Which of the following is an appropriate description of the lubricating oil film used for engine bearings?

Choices:

• A. The oil film thickness increases as the load increases
• B. ✅ The higher the rotation speed, the higher the oil film pressure
• C. The lower the oil viscosity, the thicker the oil film
• D. If the oil film breaks, the metal temperature decreases

Explanation:

As the rotation speed of the bearing increases, the action of drawing in oil becomes stronger, and the oil film pressure increases. This improves the ability to support the load.

Question: Which of the following is inappropriate as a measure to prevent engine detonation (knocking)?

Choices:

• A. ✅ Advancing the ignition timing
• B. Using fuel with a high octane rating
• C. Removing carbon deposits in the combustion chamber
• D. Lowering the intake air temperature

Explanation:

Advancing the ignition timing causes combustion to start during the compression stroke, increasing the temperature and pressure at the end of compression, which makes knocking more likely to occur. To prevent knocking, it is necessary to retard the ignition timing.

Problem: Which of the following is appropriate as a description of the engine oil viscosity index?

Options:

• A. The higher the viscosity index, the greater the viscosity change with temperature
• B. Multigrade oil has a lower viscosity index than single-grade oil
• C. ✅ High-viscosity index oil can balance low-temperature startability and high-temperature lubricity
• D. The viscosity index is an indicator of the oil's cleaning properties

Explanation:

Oil with a high viscosity index has small viscosity changes due to temperature, so it has good startability at low temperatures and can maintain appropriate viscosity to maintain lubricity at high temperatures. Multigrade oils have a high viscosity index.

Problem: Which of the following is inappropriate as a description of the engine flywheel?

Options:

• A. The flywheel smooths out the rotational fluctuations of the crankshaft
• B. ✅ The larger the moment of inertia of the flywheel, the better the engine response
• C. A ring gear is attached to the flywheel
• D. The flywheel serves as the mounting surface for the clutch

Explanation:

The larger the moment of inertia of the flywheel, the smaller the fluctuation in rotation, but the responsiveness to changes in speed decreases. Conversely, if the moment of inertia is small, responsiveness improves, but rotational fluctuation increases.

Problem: Which of the following is appropriate as a description of the fuel tank canister?

Options:

• A. The canister releases fuel vapor from the fuel tank into the atmosphere
• B. ✅ The activated carbon inside the canister adsorbs fuel vapor
• C. The purge valve is always open
• D. The main purpose of the canister is to improve engine output

Explanation:

The canister adsorbs fuel vapor from the fuel tank into activated carbon to prevent its release into the atmosphere. When the engine is running, the purge valve opens, and the adsorbed fuel vapor is sent into the intake system to be burned.

Problem: Which of the following is inappropriate as a description of the injector's injection method?

Options:

• A. The port injection method injects fuel near the intake port of each cylinder
• B. The in-cylinder direct injection method injects fuel directly into the combustion chamber
• C. ✅ The sequential injection method injects fuel into all cylinders simultaneously
• D. The in-cylinder direct injection method allows for a higher compression ratio

Explanation:

The sequential injection method injects fuel in order according to the intake stroke of each cylinder. Injecting into all cylinders simultaneously is either the group injection method or the simultaneous injection method.

Problem: Which of the following is appropriate as a measure to reduce NOx in exhaust gas?

Options:

• A. Increase the combustion temperature
• B. ✅ Return a portion of the exhaust gas to the intake side using an EGR device
• C. Enrich the air-fuel ratio
• D. Advance the ignition timing

Explanation:

The EGR (Exhaust Gas Recirculation) device reduces the combustion temperature by returning a portion of the exhaust gas to the intake side, thereby suppressing the generation of NOx. Since NOx increases as the combustion temperature rises, lowering the temperature is effective.

Problem: Which of the following is inappropriate as a description of the operation of the variable intake valve timing mechanism?

Options:

• A. In the low-speed range, overlap is reduced to increase volumetric efficiency
• B. In the high-speed range, overlap is increased to improve output
• C. The phase of the camshaft is changed by hydraulic pressure
• D. ✅ Even if the valve timing is changed, the valve lift amount changes

Explanation:

The variable valve timing mechanism changes the valve opening and closing timing by changing the phase of the camshaft, but the valve lift amount itself does not change. To change the lift amount, a separate variable valve lift mechanism is required.

Problem: Which of the following is appropriate as a description of the turbocharger wastegate valve?

Options:

• A. ✅ The wastegate valve opens when the boost pressure exceeds a specified value
• B. If the wastegate valve is always open, the boost pressure increases
• C. The wastegate valve is provided on the intake side
• D. A failure of the wastegate valve does not affect the boost pressure

Explanation:

The wastegate valve opens when the boost pressure exceeds a specified value and bypasses a portion of the exhaust gas around the turbine to limit the boost pressure. This keeps the boost pressure within the proper range.

Problem: Which of the following is inappropriate as a description of the intake air temperature sensor?

Options:

• A. The lower the intake air temperature, the higher the density of the intake air
• B. In thermistor-type sensors, the resistance value decreases as the temperature rises
• C. The intake air temperature signal is used to correct the fuel injection amount
• D. ✅ A failure of the intake air temperature sensor does not affect engine performance

Explanation:

If the intake air temperature sensor fails, the ECU cannot accurately detect the intake air temperature, and the correction of the fuel injection amount will not be performed properly, affecting the engine's startability, power output, and fuel efficiency.

Problem: Which of the following is appropriate as a description of the stator coil of an alternator?

Options:

• A. The stator coil is the rotating part
• B. ✅ Three-phase alternating current is generated in the stator coil
• C. The stator coil generates direct current
• D. Brushes are used for the stator coil

Explanation:

The stator coil of an alternator is fixed, and three-phase alternating current is generated by the rotation of the rotor. This three-phase alternating current is rectified into direct current by diodes.

Problem: Which of the following is inappropriate as a description of the primary current control of the ignition coil?

Options:

• A. The longer the energization time, the more energy is stored in the coil
• B. ✅ At high speeds, it is necessary to shorten the energization time
• C. If the primary current is cut off before reaching its maximum value, the secondary voltage decreases
• D. If the energization time is excessive, the ignition coil will overheat

Explanation:

At high speeds, as the time per cycle becomes shorter, it is necessary to advance the energization start timing to secure enough energization time. If the energization time is too short, sufficient energy cannot be stored in the coil, leading to a decrease in ignition performance.

Problem: Which of the following is appropriate as a description of the cam angle sensor?

Options:

• A. ✅ The cam angle sensor detects the rotational position of the camshaft
• B. The signals from the cam angle sensor are not used for ignition timing control
• C. The engine will start normally even if the cam angle sensor fails
• D. The cam angle sensor is mounted on the crankshaft

Explanation:

The cam angle sensor detects the rotational position of the camshaft and determines which cylinder is at the compression top dead center. Based on this signal, the ECU performs accurate cylinder identification and sequential injection control.

Problem: Which of the following is inappropriate as a description of the ECU's learning function?

Options:

• A. The learning function allows for adaptation to the aging of the engine
• B. When the battery is removed, the learned values are reset
• C. Idle speed learning is updated according to operating conditions
• D. ✅ The learning function automatically repairs sensor failures

Explanation:

The ECU's learning function optimizes control in response to engine aging and individual differences, but it cannot repair the sensor failure itself. If a sensor fails, physical replacement is necessary.

Problem: Which of the following descriptions regarding the vehicle speed sensor is appropriate?

Choices:

• A. ✅ The vehicle speed sensor detects the rotation speed of the transmission output shaft
• B. The vehicle speed sensor signal is used only for the speedometer
• C. Failure of the vehicle speed sensor does not affect fuel injection control
• D. A mechanical cable is used for the vehicle speed sensor

Explanation:

The vehicle speed sensor detects the rotation speed of the transmission output shaft or differential to calculate the vehicle speed. This signal is used not only for the speedometer display but also for fuel injection control, AT shift control, ABS control, etc.

Problem: Which of the following descriptions regarding the internal resistance of the battery is inappropriate?

Choices:

• A. As the battery deteriorates, internal resistance increases
• B. If the internal resistance is large, the voltage drop during high-current discharge will be large
• C. ✅ The lower the temperature, the smaller the internal resistance
• D. An increase in internal resistance leads to a decrease in starting performance

Explanation:

When the temperature of the battery becomes low, the viscosity of the electrolyte increases, hindering the movement of ions, thus the internal resistance increases. This results in a decrease in starting performance at low temperatures.

Problem: Which of the following descriptions regarding the characteristics of CAN communication is appropriate?

Choices:

• A. In CAN communication, each ECU is connected by individual wiring
• B. In CAN communication, multiple ECUs can send and receive data simultaneously
• C. ✅ Termination resistors are required at both ends
• D. The larger the potential difference between CAN-H and CAN-L, the lower the noise immunity

Explanation:

In CAN communication, termination resistors (typically 60Ω) are installed at both ends of the bus line (CAN-H and CAN-L) to prevent signal reflection and ensure communication reliability.

Problem: Which of the following descriptions regarding the starter's overrunning clutch is appropriate?

Choices:

• A. ✅ Protects the starter until the pinion gear disengages from the ring gear after the engine starts
• B. The overrunning clutch transmits power in both directions
• C. If the overrunning clutch fails, the starter will stop functioning
• D. An electromagnetic type is used for the overrunning clutch

Explanation:

The overrunning clutch protects the starter's armature from over-rotation by cutting off reverse drive to the starter side when the engine's rotation exceeds the starter's rotation after the engine starts.

Problem: Which of the following descriptions regarding the diagnosis of the charging system is inappropriate?

Choices:

• A. Charging voltage is measured at the battery terminals while the engine is running
• B. If the charging voltage is always below 12V, insufficient charging is likely
• C. If the charging voltage exceeds 16V, regulator failure is likely
• D. ✅ A loose belt does not cause a charging failure

Explanation:

If the alternator drive belt is loose, the alternator will not be driven at a sufficient rotation speed, causing the amount of power generated to decrease and leading to a charging failure. The belt tension directly affects the charging performance.

Problem: Which of the following descriptions regarding the starter relay (magnet switch) is appropriate?

Choices:

• A. ✅ The magnet switch opens and closes the starter's high-current circuit using a small current
• B. The pull-in coil and hold coil of the magnet switch have the same role
• C. If the magnet switch fails, the battery will go dead
• D. The magnet switch does not have a function to push out the pinion gear

Explanation:

The magnet switch activates an electromagnet by a small current signal from the ignition switch, opening and closing the high-current circuit to the starter. At the same time, it also has the role of pushing the pinion gear into the ring gear.

Problem: Which of the following descriptions regarding battery specific gravity measurement is inappropriate?

Choices:

• A. A hydrometer is used to measure the specific gravity of the electrolyte
• B. The specific gravity at full charge is approximately 1.280
• C. ✅ The lower the specific gravity, the better the state of charge
• D. If there is a large difference in specific gravity between each cell, battery deterioration is suspected

Explanation:

The lower the specific gravity of the electrolyte, the poorer the state of charge of the battery. When it approaches a full discharge, the specific gravity drops to about 1.120. Conversely, the higher the specific gravity, the better the state of charge.

Problem: Which of the following descriptions regarding the counter gear of a manual transmission is appropriate?

Choices:

• A. ✅ The counter gear is constantly in mesh with the input shaft
• B. The counter gear rotates only during gear shifting
• C. The counter gear is used only for reverse
• D. The number of teeth on the counter gear does not affect the gear ratio

Explanation:

The counter gear is constantly in mesh with the gear on the input shaft and is always rotating by receiving power from the engine. During gear shifting, it is connected to the gears of each gear stage via the synchromesh mechanism on the output shaft.

Problem: Which of the following descriptions regarding clutch judder is inappropriate?

Choices:

• A. Caused by oil contamination on the friction surface of the clutch disc
• B. A phenomenon where the vehicle vibrates when the clutch is engaged
• C. Caused by distortion of the pressure plate
• D. ✅ Occurs when the clutch pedal free play is excessive

Explanation:

Judder is a vibration that occurs when the clutch is engaged due to uneven contact of the clutch friction surfaces. The main causes include oil contamination on the disc, distortion of the pressure plate, and distortion of the flywheel. It has little relationship with pedal free play.

Problem: Which of the following descriptions regarding the band brake of an automatic transmission (AT) is appropriate?

Choices:

• A. The band brake performs braking by tightening from the outside of the drum
• B. The band brake is not operated by hydraulic pressure
• C. ✅ The servo piston generates the tightening force for the band brake
• D. The band brake is used as a parking brake

Explanation:

The band brake operates when the servo piston is activated by hydraulic pressure, tightening the band around the drum from the outside to apply braking. It has the role of fixing specific elements (such as the sun gear or planetary carrier) at specific gear stages.

Problem: Which of the following descriptions regarding CVT pulley hydraulic control is inappropriate?

Choices:

• A. Controls the primary pulley's hydraulic pressure to change the gear ratio
• B. Secondary pulley hydraulic pressure is necessary to prevent belt slippage
• C. If hydraulic pressure is insufficient, the belt will slip
• D. ✅ Pulley hydraulic pressure is controlled only by engine speed

Explanation:

CVT pulley hydraulic pressure is controlled by the ECU based on multiple conditions, including throttle opening, vehicle speed, and driving mode (D, S, L, etc.), not just engine speed. This achieves the optimal gear ratio and belt tension.

Question: Which of the following is an appropriate description of the center bearing of the propeller shaft?

Options:

• A. The center bearing supports a propeller shaft that is divided into two parts
• B. When the center bearing deteriorates, vibration and abnormal noise occur
• C. Grease is sealed within the center bearing
• D. ✅ All of the above are appropriate

Explanation:

The center bearing supports the middle section of a long propeller shaft that has been divided into two. Grease is sealed in the ball bearing, and its deterioration causes vibration and abnormal noise. All descriptions are appropriate.

Question: Which of the following is an inappropriate description of constant velocity joints (CV joints)?

Options:

• A. Constant velocity joints can transmit power at a constant speed even when angled
• B. They are used in the drive shafts of front-wheel-drive vehicles
• C. If the boot is torn, grease will scatter, causing abnormal noise or damage
• D. ✅ Constant velocity joints are used only in the propeller shafts of rear-wheel-drive vehicles

Explanation:

Constant velocity joints are mainly used in the drive shafts of front-wheel-drive and four-wheel-drive vehicles, but they may also be used in the propeller shafts of some rear-wheel-drive vehicles. Therefore, the description "only" is inappropriate.

Question: Which of the following is an appropriate description of the anti-dive mechanism of the suspension?

Options:

• A. ✅ Anti-dive suppresses the sinking of the front part of the vehicle body during braking
• B. Anti-dive prevents lateral leaning during turning
• C. The anti-dive mechanism is only adopted for the rear suspension
• D. The anti-dive effect is unrelated to suspension geometry

Explanation:

The anti-dive mechanism suppresses the nose-down posture change (dive) that occurs in the front suspension during braking through the design of the suspension geometry. This improves stability during braking.

Question: Which of the following is an inappropriate description of the oil pump for hydraulic power steering?

Options:

• A. The oil pump is driven by the engine
• B. Vane-type pumps are widely used
• C. The discharge volume of the pump is proportional to the engine speed
• D. ✅ Even if the pump fails, it does not affect the steering operation at all

Explanation:

If the oil pump fails, the power steering assist function is lost, making the steering operation extremely heavy. However, manual operation itself is still possible.

Question: Which of the following is an appropriate description of the brake fade phenomenon?

Options:

• A. ✅ Fade phenomenon is a phenomenon in which the friction material overheats due to brake use, causing the coefficient of friction to decrease
• B. When the fade phenomenon occurs, the braking force improves
• C. The fade phenomenon is caused by the boiling of brake fluid
• D. The fade phenomenon does not occur when using brakes on long downhill slopes

Explanation:

The fade phenomenon is a phenomenon in which the friction material (pads or linings) overheats due to continuous brake use, causing the coefficient of friction to decrease and the braking force to drop. It is likely to occur on long downhill slopes.

Question: Which of the following is an inappropriate description of brake fluid characteristics?

Options:

• A. Brake fluid is hygroscopic and therefore requires regular replacement
• B. ✅ If water enters the brake fluid, the boiling point rises
• C. DOT standards define performance criteria for brake fluid
• D. Brake fluid is required to have compatibility with rubber parts

Explanation:

If moisture enters the brake fluid, the boiling point decreases. When the boiling point decreases, the brake fluid becomes easier to boil due to the heat generated during brake use, increasing the danger of causing the vapor lock phenomenon.

Question: Which of the following is an appropriate description of brake squeal in disc brakes?

Options:

• A. ✅ Brake squeal occurs due to resonance between the pads and the rotor
• B. Brake squeal is not a problem because it does not affect braking force
• C. Chamfering of pads or installation of shims has no effect on preventing squeal
• D. Brake squeal does not occur with new pads

Explanation:

Brake squeal occurs when resonance is generated at a specific frequency due to frictional vibration between the brake pads and the disc rotor. Measures such as pad chamfering, shim installation, and grease application serve as anti-squeal measures.

Question: In light of the "Road Transport Vehicle Safety Standards," which of the following is an inappropriate description of headlamps?

Options:

• A. The high beam must be able to confirm obstacles in traffic at a distance of 100m at night
• B. The low beam is distributed so as not to interfere with other traffic
• C. The color of the headlamp light is white or pale yellow
• D. ✅ The number of headlamps must be 4 or more

Explanation:

The number of headlamps is stipulated as 2 or 4, combining the high beams and low beams. The description stating 4 or more is inappropriate.

Question: In light of the "Road Transport Vehicle Safety Standards," which of the following is an appropriate description of the braking capability of the braking system?

Options:

• A. The service brake system must be able to stop within 12m when braked from 50km/h on a dry, level, paved road surface
• B. The parking brake system must be able to hold the vehicle in a stationary state on a slope with a 20% gradient
• C. Braking systems must be arranged in a position where they can be easily operated while driving
• D. ✅ All of the above are appropriate

Explanation:

Safety standards stipulate the braking capability of the service brake system (within 12m from 50km/h), the holding capability of the parking brake system (20% gradient), operability, etc. All descriptions comply with the safety standards.

Question: Which of the following is an inappropriate description of diagnosis using an engine vacuum gauge?

Options:

• A. Intake negative pressure during idling serves as an indicator to judge the engine condition
• B. ✅ If the negative pressure is lower than the standard value, a leak in the intake system is possible
• C. If the negative pressure is higher than the standard value, a blockage in the exhaust system is possible
• D. A shift in valve timing appears as fluctuations in negative pressure

Explanation:

If there is a leak in the intake system, extra air enters, causing the intake negative pressure to be higher (vacuum level is lower) than the standard value. Negative pressure being lower than the standard value (vacuum level is higher) is caused by blockages in the exhaust system, etc.

Question: Which of the following is an appropriate description of the OBD (On-Board Diagnostics) system?

Options:

• A. The OBD system detects abnormalities in various sensors and actuators
• B. A diagnostic code is a number that identifies the content of a failure
• C. The MIL (Malfunction Indicator Lamp) lights up when a failure is detected
• D. ✅ All of the above are appropriate

Explanation:

The OBD system monitors various systems of the vehicle, detects abnormalities, and records them as diagnostic codes. If a serious failure is detected, the MIL (malfunction indicator lamp, check engine lamp) lights up to notify the driver. All descriptions are appropriate.