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Quizzes > Lifestyle & Hobbies

Automotive Knowledge Test: Engines, Safety, and Diagnostics

Quick, free car knowledge test to check fundamentals. Instant results.

Editorial: Review CompletedCreated By: Sarah Chen LinUpdated Aug 27, 2025
Difficulty: Moderate
Questions: 20
Learning OutcomesStudy Material
Colorful paper art depicting a car and tools for an Automotive Knowledge Test quiz

This automotive knowledge test helps you check your grasp of engines, safety, and basic diagnostics in 15 quick multiple-choice questions. See where you stand before class, shop work, or certification, and use the feedback to guide study. For focused practice, try our automotive safety test or the car mechanic quiz.

What is the primary function of the piston in an internal combustion engine?
To distribute engine oil evenly
To control the air - fuel mixture entering the cylinder
To transfer pressure from combustion gases into mechanical motion
To reduce exhaust emissions
The piston moves up and down within the cylinder, converting the pressure produced by combustion into rotational force on the crankshaft. This mechanical motion is essential for driving the engine's output.
Which component regulates coolant flow to maintain optimal engine temperature?
Oil filter
Thermostat
Carburetor
Exhaust manifold
The thermostat opens and closes to control coolant circulation through the radiator, keeping engine temperature within the desired operating range. This regulation prevents overheating and promotes efficient combustion.
What is the primary role of the vehicle's battery?
Regulate voltage output from the alternator
Reduce harmful exhaust emissions
Provide electrical energy to start the engine
Filter impurities in engine oil
The battery supplies the initial electrical power needed to crank the starter motor and start the engine. Once running, the alternator takes over to power electrical systems and recharge the battery.
Which device is responsible for reducing harmful exhaust emissions by converting pollutants into less harmful gases?
Muffler
Turbocharger
Oil cooler
Catalytic converter
The catalytic converter uses catalysts like platinum and palladium to chemically convert toxic gases such as CO, NOₓ, and hydrocarbons into less harmful substances like CO₂, N₂, and H₂O. It is a key component for meeting emission standards.
Which tool is specifically used to read onboard diagnostic trouble codes from modern vehicles?
Feeler gauge
OBD-II scanner
Torque wrench
Compression tester
An OBD-II scanner interfaces with the vehicle's diagnostic port to retrieve stored fault codes and live data. This tool is essential for identifying issues detected by the vehicle's ECU.
What is the purpose of a crankshaft position sensor in an engine management system?
To measure coolant temperature
To control exhaust gas recirculation
To monitor the position and rotational speed of the crankshaft
To regulate fuel pressure
The crankshaft position sensor provides critical data on crankshaft angle and RPM to the ECU. This information is used to precisely time fuel injection and ignition events for optimal engine performance.
How does an alternator produce DC output for the vehicle's electrical system?
It produces pure DC directly
It stores energy and releases it as DC
It uses a transformer to convert AC to DC
It generates AC and then rectifies it to DC through diodes
An alternator's rotor creates a rotating magnetic field that induces AC in the stator windings. A built-in diode rectifier then converts this AC to DC to charge the battery and power electrical loads.
What is the main function of the anti-lock braking system (ABS)?
Prevent wheel lockup during hard braking
Automatically apply brakes when reversing
Increase braking force under normal conditions
Regulate brake fluid temperature
ABS monitors wheel speed and modulates brake pressure to prevent wheel lockup. This maintains steering control and reduces stopping distance on slippery surfaces.
Which sensor measures the oxygen content in exhaust gases to help control the air - fuel mixture?
Throttle position sensor
Manifold absolute pressure sensor
Mass air flow sensor
Oxygen (O₂) sensor
The O₂ sensor monitors the level of oxygen in the exhaust stream. The ECU uses this data to adjust fuel injection for an optimal air - fuel ratio and lower emissions.
What is the primary benefit of regularly rotating tires on a vehicle?
Enhance brake pad lifespan
Promote even tire wear and extend tire life
Improve engine cooling efficiency
Optimize fuel injector performance
Rotating tires changes their positions so all tires wear evenly over time. This practice prevents premature wear on specific tires and maximizes overall tire lifespan.
When diagnosing an engine misfire, which component should be checked first?
Fuel filter clogging
Tire pressure levels
Condition of the spark plugs
Coolant temperature sensor
Spark plugs are often the source of misfires when fouled or worn, as they cannot create a proper spark. Checking their condition is a quick diagnostic step before deeper investigation.
What is the role of the engine control unit (ECU) in modern vehicles?
Filter engine oil
Directly inject fuel without sensors
Process sensor inputs and control actuators for engine operation
Only charge the battery during operation
The ECU collects data from numerous sensors, computes the optimum parameters, and commands actuators like fuel injectors and ignition coils. This ensures efficient and safe engine performance.
Which European emission standard currently imposes the strictest limits on NOₓ for passenger cars?
Euro 5
Euro 4
Euro 6
Euro 3
Euro 6 is the latest standard for passenger vehicles in Europe, setting significantly lower NOₓ and particulate limits compared to its predecessors. It targets cleaner air quality.
What is the typical resting voltage of a fully charged 12 V automotive battery?
12.6 volts
14.4 volts
11.8 volts
13.8 volts
A fully charged 12 V lead - acid battery rests at about 12.6 V when the engine is off. Voltages significantly lower indicate a partially discharged or aging battery.
Which tool is most appropriate for testing continuity in a vehicle's wiring harness?
Scan tool
Digital multimeter in continuity mode
Torque wrench
Oscilloscope
A digital multimeter set to continuity checks resistance through a wire, indicating if the circuit is intact. It's the standard tool for diagnosing wiring faults.
During an OBD-II diagnosis, which parameter indicates a lean condition in the fuel mixture?
Mass air flow reading is above expected
Short-term fuel trim significantly positive
Short-term fuel trim significantly negative
O₂ sensor voltage is high
A positive short-term fuel trim means the ECU is adding more fuel to compensate for a detected lean condition. This adjustment helps maintain the target air - fuel ratio.
What reagent is injected into the exhaust stream in a selective catalytic reduction (SCR) system to reduce NOₓ emissions?
Diesel fuel
Methanol
Aqueous urea solution (AdBlue)
Engine oil
SCR systems use a urea-water solution (commonly known as AdBlue) that decomposes into ammonia, which reacts with NOₓ over a catalyst to form nitrogen and water, reducing emissions.
In a CAN bus network, what is the typical termination resistance value at each end of the bus?
100 ohms
240 ohms
10 ohms
120 ohms
A CAN bus requires two 120 Ω termination resistors at each end to match impedance and prevent signal reflections. Proper termination ensures reliable communication.
A diesel engine cylinder shows 300 psi on a compression test when the specification is 500 psi. Which is the most likely cause?
Weak battery
Worn piston rings
Clogged fuel injector
Dirty air filter
Low compression in a diesel cylinder is commonly due to worn piston rings or cylinder wall wear, allowing air to escape during compression. Other faults would not directly reduce mechanical compression.
If an engine with a 2.0 L displacement draws 1.6 L of air per cycle under test conditions, what is its volumetric efficiency?
80%
90%
100%
60%
Volumetric efficiency is the ratio of actual air volume inducted to the engine's theoretical displacement. Here, 1.6 L divided by 2.0 L equals 0.80 or 80%.
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Learning Outcomes

  1. Identify major engine components and functions.
  2. Analyse vehicle electrical and electronic systems.
  3. Evaluate automotive safety and emission standards.
  4. Apply diagnostic principles to detect common faults.
  5. Master maintenance procedures for optimal performance.
  6. Demonstrate knowledge of automotive industry terminology.

Cheat Sheet

  1. Core Engine Components - Engines are like symphonies of metal parts! Cylinders, pistons, crankshafts, camshafts, and valves team up to convert fuel into the mechanical energy that powers your ride. Understanding how each piece fits together helps you troubleshoot and tune like a pro.
  2. Engine Control Unit (ECU) - Think of the ECU as your engine's brain: it controls fuel injection, ignition timing, and more to maximize performance and efficiency. A well-tuned ECU makes the difference between sluggish starts and spirited acceleration. Dive in to see how this little computer keeps everything running smoothly.
  3. On-Board Diagnostics (OBD) Systems - OBD systems are your car's self-checking mechanism, constantly monitoring performance and emissions. When something goes wrong, they spit out trouble codes (DTCs) that point you to the issue. Learning to read these codes is like having a mechanic in your pocket!
  4. Automotive Electronics - Modern vehicles rely on a network of sensors and actuators to keep you safe and comfortable. From airbag deployment to throttle control, electronics are everywhere under the hood. Exploring these components will make you appreciate how tech-savvy cars have become.
  5. Vehicle Electrical Systems - The battery, alternator, and starter motor form the electrical backbone of your car. They get the engine running and power lights, infotainment, and more. Grasping these basics ensures you never get stranded with a dead battery!
  6. Emission Control Systems - Catalytic converters, EGR valves, and other gadgets work tirelessly to scrub harmful pollutants from your exhaust. They help cars meet strict environmental laws and keep the air cleaner. Mastering these systems is key for anyone aiming to build or maintain eco-friendly vehicles.
  7. Diagnostic Principles - Beyond OBD codes, real diagnostics blend data reading with hands-on testing: voltage checks, pressure measurements, and smoke tests. Learning to wield scanners and multimeters turns guessing into precision troubleshooting. Every great mechanic starts with smart diagnostics!
  8. Routine Maintenance Procedures - Simple tasks like oil changes, brake inspections, and tire rotations dramatically extend your vehicle's life. Staying ahead of wear and tear saves you money and headaches down the road. Embrace these routines to keep your ride in tip-top shape!
  9. Automotive Industry Terminology - Words like torque, horsepower, and drivetrain become second nature once you know their meanings. This glossary helps you decode spec sheets and speak confidently with fellow gearheads. A solid vocabulary is the foundation of mastery!
  10. Evolution of Automotive Technology - From purely mechanical beginnings to today's advanced electronic controls, cars have transformed dramatically. Understanding this history gives you perspective on current innovations and future trends. It's a turbocharged journey through time!
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