I85PREP
⌘ K
Craftsman Motor Vehicles Maintenance study materials
Craftsman Motor Vehicles Maintenance study resources

Craftsman Motor Vehicles Maintenance practice questions

One question at a time. Build your Craftsman Motor Vehicles Maintenance understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Safety, Tools, and Workshop Practice

Before sliding under a vehicle supported only by a hydraulic trolley jack, a technician should ensure the vehicle is also supported by:

  1. Wooden blocks placed under the tyres
  2. The vehicle's parking brake alone
  3. A second trolley jack placed under the opposite side
  4. Jack stands placed under the manufacturer's specified lift points Correct answer.

Explanation

A hydraulic jack is a lifting device, not a support device; it can lose pressure suddenly. The vehicle must be lowered onto rated jack stands positioned at the manufacturer's designated support points before any work begins underneath. Wheel chocks and the parking brake stop the vehicle rolling but do not prevent it from dropping.

Question 2Safety, Tools, and Workshop Practice

When charging a lead-acid battery in the workshop, which precaution directly reduces the risk of a hydrogen explosion?

  1. Charging with the filler caps removed and the charger set to boost
  2. Disconnecting the charger while it is still switched on
  3. Charging in a well-ventilated area away from sparks and flames Correct answer.
  4. Placing the battery on a metal bench to earth it

Explanation

Lead-acid batteries release hydrogen during charging, and a concentration of only a few percent in air is explosive. Good ventilation disperses the gas, and keeping ignition sources away removes the trigger. Disconnecting a live charger or creating sparks near the vents can ignite the gas.

Question 3Safety, Tools, and Workshop Practice

A torque wrench has been dropped onto the workshop floor. What is the correct action before returning it to service?

  1. Oil the adjustment mechanism and continue using it
  2. Use it only for lower torque values to be safe
  3. Tap it lightly to check the ratchet still clicks
  4. Recalibrate or verify it against a known reference and record the result Correct answer.

Explanation

A drop can bend the beam or disturb the internal spring, so indicated torque may no longer match actual torque. Verification against a calibrated reference confirms whether the tool is still within tolerance. Using it on critical fasteners without checking risks under- or over-tightening.

Question 4Safety, Tools, and Workshop Practice

The correct way to store a click-type torque wrench between jobs is to:

  1. Hang it by the drive square from a hook
  2. Store it fully wound to the maximum setting
  3. Leave it set at the last torque used
  4. Set it to its lowest scale value and keep it in its case Correct answer.

Explanation

Click-type wrenches contain a spring that is compressed when set to a torque value. Storing at the lowest setting relieves that load and preserves calibration over time. Hanging by the drive or leaving it wound keeps stress on the mechanism.

Question 5Safety, Tools, and Workshop Practice

Which item of personal protective equipment is most important when using a compressed-air blow gun to dry components?

  1. Steel-toe boots
  2. Cut-resistant gloves
  3. Impact-rated eye protection Correct answer.
  4. Flame-retardant overalls

Explanation

Compressed air can throw metal particles, brake dust and fluid droplets at high speed. Impact-rated eye protection is the primary barrier against eye injury in this task. The other items protect against hazards that are not the main risk of air blowing.

Question 6Safety, Tools, and Workshop Practice

A CO2 extinguisher is the appropriate first response to which workshop situation?

  1. A pan of burning oil on a bench
  2. A person's clothing that has caught fire
  3. A fire in a magnesium component on the bench
  4. A small fire in a live electrical panel Correct answer.

Explanation

CO2 does not conduct electricity and leaves no residue, so it suits small fires involving energised electrical equipment. It also starves the fire of oxygen without damaging the panel. Other situations call for different media or actions.

Question 7Safety, Tools, and Workshop Practice

Under typical workshop practice, waste engine oil should be:

  1. Poured into the general refuse bin once cooled
  2. Drained into the designated waste-oil tank for licensed collection Correct answer.
  3. Mixed with used coolant and stored in one drum
  4. Poured down a drain with plenty of water

Explanation

Used engine oil is a controlled waste and must go into the dedicated container for authorised collection. Mixing it with other fluids or disposing of it through drains contaminates watercourses and breaches environmental rules.

Question 8Safety, Tools, and Workshop Practice

When raising a vehicle on a two-post lift, the arms should be positioned so that:

  1. The arms sit as far inboard as possible under the floor pan
  2. Only two arms are used for a lighter vehicle
  3. Each arm contacts the manufacturer's designated lift point with the vehicle balanced Correct answer.
  4. The pads press on the plastic sill covers

Explanation

Lift points are reinforced areas designed to carry the vehicle's weight. Using them with the load balanced prevents the vehicle tipping or the body deforming. Sill covers and floor pans are not structural lifting points.

Question 9Safety, Tools, and Workshop Practice

A technician is about to remove a fuel tank from a vehicle with a plastic tank and an in-tank electric pump. Which preparation step is essential?

  1. Disconnect the pump wiring while the ignition is on to confirm the circuit
  2. Run the engine until it stops to empty the lines
  3. Loosen the fuel cap slowly and begin work immediately
  4. Relieve fuel system pressure and disconnect the battery earth before opening the lines Correct answer.

Explanation

Fuel lines remain pressurised after shutdown, so pressure must be released at the specified point before a line is opened. Disconnecting the battery earth removes the risk of the pump or ignition sparking during the job. Working live or on a pressurised line can spray fuel onto hot parts.

Question 10Safety, Tools, and Workshop Practice

When using an angle grinder fitted with a cutting disc, the guard should be:

  1. Fitted and adjusted so it sits between the operator and the disc Correct answer.
  2. Replaced with a wire cup brush guard
  3. Left loose so it can self-align
  4. Removed to allow better access in tight areas

Explanation

The guard is designed to stop fragments and sparks being thrown at the operator if the disc shatters. It must be fitted and rotated to face the work so the open section is away from the body. Removing or loosening it defeats the protection.

Question 11Safety, Tools, and Workshop Practice

Which practice best prevents a hand tool such as a spanner from slipping and injuring the technician?

  1. Apply force with the handle greasy to improve grip
  2. Stand directly over the fastener and push down
  3. Use an extension pipe on a combination spanner
  4. Pull the handle toward the body rather than pushing it away Correct answer.

Explanation

Pulling toward the body keeps the technician's weight controlled if the fastener suddenly releases. A slip then moves the hand away from the work rather than driving it into sharp edges. Pushing or overloading the tool increases the chance of a sudden slip.

Question 12Safety, Tools, and Workshop Practice

A compressed-air line in the workshop is fitted with a filter-regulator-lubricator unit. What is the main purpose of the lubricator section?

  1. To add a fine oil mist that protects air tools from wear Correct answer.
  2. To filter solid particles from the air stream
  3. To remove water from the air before it reaches the tool
  4. To regulate the delivery pressure to the tool

Explanation

The lubricator injects a controlled oil mist into the downstream air so pneumatic motors and cylinders stay lubricated. The filter removes solids and water, while the regulator sets pressure. Each section of the unit performs a separate function.

Question 13Safety, Tools, and Workshop Practice

During a road test a technician notices the brake pedal slowly sinking to the floor while held at a constant pressure. Which action is the correct immediate response?

  1. Continue the test at higher speed to confirm the fault
  2. Ignore it because some sink is normal on all vehicles
  3. Pump the pedal repeatedly to keep pressure and finish the route
  4. Return to the workshop at low speed using engine braking and inspect the hydraulic system Correct answer.

Explanation

A pedal that sinks under steady pressure indicates a hydraulic leak, often past a seal or from a corroded line. Braking performance may be lost without warning, so the test must be abandoned safely and the system inspected. Pumping the pedal masks the fault and extends exposure to risk.

Question 14Safety, Tools, and Workshop Practice

When working near a supplemental restraint system, the recommended waiting period after disconnecting the battery is intended to:

  1. Let the battery cool before reconnection
  2. Give the engine management system time to relearn idle
  3. Allow the backup capacitor in the airbag control module to discharge Correct answer.
  4. Allow the fuel system to depressurise

Explanation

Airbag modules store enough energy in a capacitor to fire a squib for a short time after the battery is removed. The manufacturer's waiting time lets that charge bleed off so the circuit is inert before connectors are disturbed. It is not related to cooling or fuel pressure.

Question 15Safety, Tools, and Workshop Practice

A vehicle with a high-voltage traction battery is being raised for underbody work. Which precaution applies to the technician?

  1. Cut the orange cables to remove the battery quickly
  2. Wear cotton gloves as the only electrical protection
  3. Treat all orange-coded cables as live and isolate the system per the manufacturer's procedure Correct answer.
  4. Assume the system is dead once the ignition is off

Explanation

High-voltage cables are colour-coded orange and remain dangerous until the system is formally isolated and verified dead. The manufacturer's shutdown procedure includes waiting times and verification with a suitable meter. Ignition-off alone does not guarantee the pack is de-energised.

Question 16Safety, Tools, and Workshop Practice

Which is the correct method for checking the level of coolant in a sealed system with a pressurised expansion tank?

  1. Squeeze the top hose with the engine running to judge the level
  2. Open the cap while the engine is at full operating temperature
  3. Rely on the dashboard temperature gauge alone
  4. Check the level markings with the engine cold before opening the cap Correct answer.

Explanation

A hot cooling system is under pressure and can release scalding coolant when the cap is opened. Checking against the markings with the engine cold is both safe and accurate. The temperature gauge shows operating temperature, not the level.

Question 17Safety, Tools, and Workshop Practice

A technician must drill a hole in a vehicle's high-strength steel body panel. Which precaution protects both the technician and the vehicle's corrosion protection?

  1. Apply heat with a torch to soften the steel before drilling
  2. Use a sharp bit at controlled speed and apply cavity wax or primer to the exposed metal Correct answer.
  3. Drill through the wiring loom channel to save time
  4. Drill at maximum speed to finish quickly and leave the edges bare

Explanation

Controlled drilling with a sharp bit limits heat and the risk of the bit snagging. Bare metal at a new hole becomes a corrosion start point, so it must be primed or waxed. High speed and heat can also damage adjacent components.

Question 18Safety, Tools, and Workshop Practice

Which is the correct way to lift a heavy component such as a cylinder head from an engine bay?

  1. Lift with one hand while steadying against the wing with the other
  2. Use a rated lifting sling or hoist and keep the load close to the body with a straight back Correct answer.
  3. Bend at the waist and twist while lifting
  4. Ask a colleague to lift the far end while you carry the near end without coordinating

Explanation

Mechanical aids remove the load from the spine, and correct posture with the load close to the body reduces strain. Twisting while lifting is a common cause of back injury. Manual handling limits should be respected.

Question 19Safety, Tools, and Workshop Practice

A bench grinder is being set up. Which adjustment is correct before use?

  1. Leave a large gap at the tool rest so parts can be fed easily
  2. Set the tool rest close to the wheel and adjust the spark guard to compensate for wear Correct answer.
  3. Remove the spark guards to see the work clearly
  4. Fit a wire wheel with the guards removed

Explanation

A small gap between the tool rest and wheel prevents parts being drawn into the nip point. The spark guard must be adjusted as the wheel wears so it stays close to the wheel face. Removing guards exposes the operator to ejected fragments.

Question 20Safety, Tools, and Workshop Practice

An engine is being run in the workshop for diagnosis. Which control most directly reduces the risk of carbon monoxide exposure?

  1. Opening a window slightly at the far end of the bay
  2. Facing the tailpipe away from the technician
  3. Connecting an extraction hose to the tailpipe and running it outdoors Correct answer.
  4. Running the engine only at idle speed

Explanation

Carbon monoxide is odourless and can build to dangerous levels quickly in an enclosed space. Local exhaust extraction at the tailpipe removes the gas at source. Idle speed and open windows reduce but do not control the hazard.

Question 21Safety, Tools, and Workshop Practice

A technician is using a multimeter to test a circuit that may be live. Which setup gives the safest and most useful first measurement?

  1. Select the current range and connect the meter in series
  2. Hold both probes by the metal tips for a better contact
  3. Select the correct voltage range and connect the common lead to a known good earth Correct answer.
  4. Select resistance and probe the circuit while it is powered

Explanation

Measuring voltage with the meter in parallel and the common lead on a good earth confirms whether the circuit is live before further work. Selecting current or resistance on a live circuit can blow the meter's fuse or damage it. Touching probe tips risks a shock.

Question 22Safety, Tools, and Workshop Practice

A vehicle on a two-post lift begins to tilt as the lift is raised. What is the correct response?

  1. Stop raising, lower the lift fully, and reposition the arms before lifting again Correct answer.
  2. Shake the vehicle to settle it onto the pads
  3. Continue raising to full height, where the locks will stabilise it
  4. Ask a colleague to hold the low side while you raise it

Explanation

Tilting shows the load is not balanced on the arms, and continuing to raise makes a fall more likely. Lowering fully and repositioning at the correct lift points restores stability. No person should stand under or steady a moving vehicle.

Question 23Safety, Tools, and Workshop Practice

A workshop stores oxygen and acetylene cylinders together. Which arrangement meets normal safe practice?

  1. Keep the cylinders near the welding bay with no chains or restraints
  2. Store both cylinders in a sealed cupboard with the regulators fitted
  3. Lay the acetylene cylinder on its side to save space
  4. Store them upright, secured, and separated by a fire-resistant barrier or distance Correct answer.

Explanation

Fuel gas and oxygen must be kept apart so a leak on one cannot feed a fire on the other. Cylinders are stored upright and restrained so they cannot fall and shear the valve. Regulators should be removed for storage.

Question 24Safety, Tools, and Workshop Practice

A technician notices the insulation on the workshop's portable inspection lamp lead is cut, exposing the inner conductors. What is the correct action?

  1. Withdraw the lamp from service, tag it as defective, and have the lead repaired or replaced Correct answer.
  2. Use the lamp only on low-voltage circuits to reduce risk
  3. Wrap the cut with insulating tape and continue using the lamp
  4. Continue using it but avoid touching the damaged section

Explanation

Damaged insulation on mains equipment is a shock and fire hazard that cannot be judged safe by the user. Withdrawing and tagging the item prevents others using it until it is properly repaired and retested. Tape repairs are not an acceptable permanent fix.

Question 25Engine Systems: Lubrication, Cooling, and Fuel

On a four-stroke engine, which component drives the oil pump on most mass-produced passenger car engines?

  1. The starter motor, through a reduction gear
  2. The crankshaft, through a gear, chain, or belt Correct answer.
  3. The alternator, through an internal shaft
  4. The camshaft, through a dedicated pushrod

Explanation

The oil pump must turn whenever the engine turns, so it is almost always driven from the crankshaft by a gear, chain, or belt, or mounted directly on the crank nose. This guarantees lubrication begins as soon as the engine is cranked. Camshaft, starter, and alternator drives do not provide that guaranteed relationship.

Question 26Engine Systems: Lubrication, Cooling, and Fuel

A vehicle's oil pressure warning lamp stays lit for several seconds after a cold start and flickers at idle when hot. Which condition most directly explains this behavior?

  1. The oil filter bypass valve is stuck open
  2. The oil pressure sending unit is reading temperature instead of pressure
  3. Oil pressure is below the switch's threshold at low engine speed Correct answer.
  4. The crankcase ventilation system is pulling oil vapor into the intake

Explanation

A warning lamp that lingers after start and flickers at hot idle indicates pressure is falling below the switch's actuation threshold, typically from worn bearings, a weak pump, diluted oil, or a restricted pickup. The switch is a simple on/off device, so the lamp reflects actual low pressure at those moments. It does not indicate a bypass valve stuck open, which would not create a low-pressure lamp at idle.

Question 27Engine Systems: Lubrication, Cooling, and Fuel

What is the primary function of the thermostat in a liquid-cooling system?

  1. To circulate coolant through the radiator
  2. To pressurize the cooling system and raise the boiling point
  3. To regulate coolant flow so the engine reaches and holds operating temperature Correct answer.
  4. To remove air bubbles from the coolant before it reaches the pump

Explanation

The thermostat is a temperature-controlled valve that stays closed during warm-up and opens progressively as coolant reaches its rated temperature. This limits flow to the radiator so the engine warms quickly and then holds a stable operating temperature. Circulation, pressurization, and deaeration are handled by other components.

Question 28Engine Systems: Lubrication, Cooling, and Fuel

A radiator cap rated at 1.1 bar (about 16 psi) is fitted to a system that specifies 0.9 bar (about 13 psi). What is the most likely consequence?

  1. The engine will run colder because pressure improves heat transfer
  2. The coolant will boil at a lower temperature than intended
  3. The cooling system will vent at a higher pressure than designed, stressing hoses and the radiator Correct answer.
  4. The water pump will cavitate because of reduced system pressure

Explanation

The cap's pressure rating sets the maximum pressure the system will hold before venting to the overflow. Fitting a higher-rated cap raises that relief point above design, increasing stress on hoses, the radiator, and the heater core. It does not change the engine's normal operating temperature or lower the boiling point.

Question 29Engine Systems: Lubrication, Cooling, and Fuel

Which fuel-delivery characteristic distinguishes a port fuel injection (PFI) system from a gasoline direct injection (GDI) system?

  1. PFI injects fuel into the intake port upstream of the intake valve; GDI injects directly into the combustion chamber Correct answer.
  2. PFI injects fuel during the compression stroke; GDI injects during the intake stroke
  3. PFI uses a low-pressure mechanical pump only; GDI uses no fuel pump at all
  4. PFI meters fuel by carburetor venturi vacuum; GDI meters fuel by throttle position alone

Explanation

In PFI the injector sprays into the intake runner, so fuel mixes with air before entering the cylinder. In GDI the injector is mounted in the cylinder head and sprays directly into the combustion chamber, usually at high pressure. The injection timing and pressure differences follow from that mounting location.

Question 30Engine Systems: Lubrication, Cooling, and Fuel

During a cylinder balance test on a gasoline engine, disabling one injector produces almost no change in engine speed or smoothness. What does this most likely indicate?

  1. The engine coolant temperature sensor is biased rich
  2. The fuel pressure regulator is stuck at high pressure
  3. That cylinder is contributing little or no power Correct answer.
  4. The ignition coil for that cylinder is firing too early

Explanation

A balance test compares how much each cylinder contributes by cutting its fuel and watching for a drop in speed or a change in smoothness. If disabling a cylinder changes nothing, that cylinder was already contributing little, pointing to a fault in its fuel, spark, or compression. The other options would affect the engine broadly rather than isolating one cylinder.

Question 31Engine Systems: Lubrication, Cooling, and Fuel

What is the purpose of the positive crankcase ventilation (PCV) valve?

  1. To release excess oil pressure from the oil galleries
  2. To meter crankcase blow-by gases into the intake for reburning Correct answer.
  3. To prevent fuel vapor from escaping the fuel tank
  4. To route exhaust gas back into the intake manifold

Explanation

The PCV valve regulates the flow of blow-by gases from the crankcase into the intake so they are burned rather than vented to atmosphere. It also helps maintain a slight vacuum in the crankcase. Fuel-tank vapor control and exhaust gas recirculation are separate systems.

Question 32Engine Systems: Lubrication, Cooling, and Fuel

A technician finds milky, emulsified oil on the dipstick and under the oil filler cap. Which condition should be investigated first?

  1. Fuel dilution from a leaking injector
  2. A restricted PCV valve causing high crankcase vacuum
  3. Excessive oil viscosity from a wrong-grade fill
  4. Coolant entering the crankcase through a failed head gasket or cooler Correct answer.

Explanation

Milky, mayonnaise-like emulsion in the oil is the classic sign of coolant mixing with oil, which points to a failed head gasket, cracked head, or a leaking oil cooler. The coolant turns the oil into an emulsion that cannot lubricate properly. Fuel dilution thins the oil but does not produce this appearance.

Question 33Engine Systems: Lubrication, Cooling, and Fuel

Which component increases the pressure of the coolant as it leaves the engine and pushes it through the radiator?

  1. The water pump Correct answer.
  2. The radiator cap
  3. The thermostat
  4. The expansion tank

Explanation

The water pump is a centrifugal impeller driven by a belt or chain, and it creates the flow and pressure that circulate coolant through the block, head, and radiator. The thermostat only controls the path and volume of that flow. The cap and expansion tank manage pressure and volume changes, not circulation.

Question 34Engine Systems: Lubrication, Cooling, and Fuel

A GDI engine develops a rough idle and misfires on one cylinder, and the injector is suspected of carbon fouling on its tip. Which service is most appropriate?

  1. Replace the spark plugs with a hotter heat range
  2. Increase fuel pressure by replacing the pressure regulator
  3. Replace the thermostat to raise operating temperature
  4. Perform an intake valve and injector cleaning service or remove and clean the injector Correct answer.

Explanation

GDI injectors sit in the combustion chamber and can accumulate carbon on the nozzle, disturbing the spray pattern and causing misfire. The appropriate repair is a targeted cleaning service or removal and cleaning or replacement of the affected injector. Spark plug heat range, fuel pressure, and thermostat changes do not address injector tip deposits.

Question 35Engine Systems: Lubrication, Cooling, and Fuel

Which statement correctly describes the relationship between oil viscosity grade and ambient temperature for engine oil selection?

  1. The second number in a multigrade oil indicates its cold-pumping ability
  2. A lower W number indicates better cold-flow behavior at low ambient temperatures Correct answer.
  3. A higher W number indicates better cold-flow behavior at low ambient temperatures
  4. Viscosity grade has no relationship to ambient starting temperature

Explanation

In a multigrade designation such as 5W-30, the number before the W describes cold-temperature performance, and a lower number means the oil flows more easily when cold. The second number describes viscosity at operating temperature. This is why cold climates call for a lower W rating.

Question 36Engine Systems: Lubrication, Cooling, and Fuel

A cooling fan that is electrically driven does not run when the engine is hot and stationary, and the engine overheats only when stopped in traffic. Which is the most likely cause?

  1. A stuck-open thermostat
  2. A leaking radiator cap
  3. A worn water pump seal
  4. A failed coolant temperature sensor or fan control circuit Correct answer.

Explanation

Overheating only when the vehicle is stationary points to a loss of airflow through the radiator, which the electric fan provides. If the fan does not run when the engine is hot, the fault is in the fan motor, relay, coolant temperature sensor, or control circuit. A stuck-open thermostat would cause overcooling, and a cap or pump seal leak would show other symptoms.

Question 37Engine Systems: Lubrication, Cooling, and Fuel

What is the function of the fuel pressure regulator on a return-type port fuel injection system?

  1. To maintain a constant pressure differential across the injectors relative to intake manifold pressure Correct answer.
  2. To increase fuel pressure as engine speed rises to match airflow
  3. To prevent fuel from draining back to the tank when the engine is off
  4. To filter particulate matter from the fuel before the injectors

Explanation

The regulator uses manifold vacuum to hold the pressure drop across the injectors nearly constant, so the fuel delivered for a given injector pulse width stays predictable as manifold pressure changes. This is why the vacuum reference line is connected to the regulator. Filtration and anti-drainback are handled by the filter and check valve.

Question 38Engine Systems: Lubrication, Cooling, and Fuel

A compression test shows one cylinder well below the others, and adding a small amount of oil to that cylinder raises the reading. What does this indicate?

  1. Worn piston rings or cylinder walls Correct answer.
  2. A leaking head gasket between two cylinders
  3. A burned exhaust valve
  4. A jumped timing chain

Explanation

Oil added to the cylinder temporarily seals the gap between the rings and the cylinder wall, so if compression rises the loss is past the rings or the bore. If the reading stays low, the leak is more likely past a valve or the head gasket. This is the classic wet-versus-dry compression comparison.

Question 39Engine Systems: Lubrication, Cooling, and Fuel

Which of the following best describes the role of the radiator's fins and tubes?

  1. To increase surface area so heat transfers from coolant to passing air Correct answer.
  2. To separate air bubbles from coolant before it returns to the pump
  3. To store extra coolant for expansion during warm-up
  4. To regulate coolant flow to the heater core

Explanation

The radiator transfers heat from the coolant to the air, and its many tubes and fins create a large surface area for that exchange. Airflow across the fins carries the heat away. Coolant storage, deaeration, and heater flow control are handled by other parts of the system.

Question 40Engine Systems: Lubrication, Cooling, and Fuel

An engine has a persistent lean condition on both banks, and a smoke test reveals a torn intake manifold gasket. How does unmetered air entering downstream of the throttle plate affect fuel trim?

  1. It causes the fuel pump to increase pressure to compensate
  2. It causes negative long-term fuel trim because the oxygen sensor reports excess fuel
  3. It has no effect on fuel trim because the mass airflow sensor already measured the air
  4. It causes positive long-term fuel trim because the oxygen sensor reports excess oxygen Correct answer.

Explanation

Air entering after the throttle plate and airflow sensor is unmetered, so the engine receives more air than the fuel calculation assumes. The oxygen sensor sees excess oxygen in the exhaust and the ECM adds fuel, producing positive fuel trim. The mass airflow sensor did not measure this air, so it cannot compensate directly.

Question 41Engine Systems: Lubrication, Cooling, and Fuel

Which of these is a normal function of the coolant recovery (overflow) bottle on a sealed cooling system?

  1. To trap combustion gases that leak into the cooling system
  2. To receive coolant pushed past the radiator cap as it expands hot and return it as the system cools Correct answer.
  3. To store a reserve of coolant that is continuously pumped through the engine
  4. To cool the coolant before it enters the radiator

Explanation

As coolant heats and expands, pressure rises until the cap relief opens and sends coolant into the recovery bottle. When the engine cools and a vacuum forms, that coolant is drawn back into the radiator, keeping the system full. It is not part of the circulation path and does not cool or filter coolant.

Question 42Engine Systems: Lubrication, Cooling, and Fuel

A technician is checking a fuel pump circuit and finds battery voltage at the pump connector during cranking but no fuel pressure at the rail. Which is the most likely cause?

  1. The inertia switch has tripped
  2. The pump motor is seized or the pump-to-tank seal has failed Correct answer.
  3. The fuel pump relay coil is open
  4. The ECM is not commanding the pump on

Explanation

Voltage present at the pump during cranking means the relay, inertia switch, and control circuit are all working, so the fault lies in the pump itself or in its ability to build pressure. A seized motor or a failed seal inside the tank would produce no rail pressure despite correct voltage. The other options would remove voltage from the pump.

Question 43Engine Systems: Lubrication, Cooling, and Fuel

Why is a coolant mixture of roughly 50 percent antifreeze and 50 percent water commonly specified?

  1. It balances freeze protection, boil-over protection, and heat transfer better than either fluid alone Correct answer.
  2. It eliminates the need for a pressure cap
  3. It minimizes the cost of coolant because water is free
  4. It prevents the thermostat from opening too quickly

Explanation

Antifreeze raises the boiling point and lowers the freeze point, while water has better heat-transfer properties than glycol. A roughly equal mix gives good protection in both directions without sacrificing too much cooling performance. Cost, thermostat behavior, and pressure-cap function are not the design basis.

Question 44Engine Systems: Lubrication, Cooling, and Fuel

A vehicle with a turbocharged gasoline engine is driven hard and then shut off immediately after a high-speed run. Which practice best protects the turbocharger's lubrication and cooling?

  1. Use a thinner oil than specified to speed cold flow
  2. Rev the engine several times before switching off
  3. Change the oil less often because turbo engines run hotter
  4. Idle the engine briefly before shutdown to let oil circulate and carry heat away Correct answer.

Explanation

After hard use the turbocharger is very hot, and oil flow through its bearings helps carry heat away. Idling briefly before shutdown keeps oil and coolant moving so the bearing housing does not soak in trapped heat, which can coke the oil in the feed line. Revving before shutdown adds heat, and oil change intervals should be shortened, not extended.

Question 45Engine Systems: Lubrication, Cooling, and Fuel

Which sensor provides the primary input the ECM uses to calculate base fuel delivery in a speed-density fuel injection system?

  1. The throttle position sensor
  2. The intake air temperature sensor
  3. The manifold absolute pressure sensor Correct answer.
  4. The oxygen sensor

Explanation

In a speed-density system, the ECM calculates airflow from engine speed and manifold absolute pressure, so the MAP sensor is the primary load input. Intake air temperature corrects the density calculation, and the oxygen sensor trims the result in closed loop. The throttle position sensor mainly indicates driver demand and rate of change.

Question 46Engine Systems: Lubrication, Cooling, and Fuel

What does an oil filter's anti-drainback valve do?

  1. It prevents oil from flowing to the cylinder head at low pressure
  2. It keeps oil in the filter and galleries so pressure builds quickly on the next start Correct answer.
  3. It opens when the filter media becomes clogged to bypass oil
  4. It relieves excess oil pressure at high engine speed

Explanation

The anti-drainback valve is a one-way flap that stops oil from draining out of the filter and oil galleries when the engine stops. This shortens the dry period on the next start and reduces wear. The bypass valve and the pressure relief valve are separate features that perform different jobs.

Question 47Engine Systems: Lubrication, Cooling, and Fuel

A scan tool shows the engine coolant temperature sensor reading stuck at about -40 degrees Celsius on a warm engine. What is the most likely effect on fuel delivery?

  1. The ECM will disable the fuel pump to protect the engine
  2. The ECM will hold the cooling fan off permanently
  3. The ECM will command a rich mixture because it believes the engine is very cold Correct answer.
  4. The ECM will command a lean mixture because it believes the engine is very hot

Explanation

A coolant temperature reading stuck at the extreme cold end tells the ECM the engine is cold, so it applies cold-start enrichment and fast idle logic. The result is a rich-running engine, poor economy, and possible fouling. A very hot reading would lean the mixture, and a cold reading would not disable the pump.

Question 48Engine Systems: Lubrication, Cooling, and Fuel

Which of the following correctly describes the purpose of exhaust gas recirculation (EGR) in a gasoline engine?

  1. It prevents detonation by cooling the fuel before injection
  2. It dilutes the intake charge to lower combustion temperature and reduce nitrogen oxide formation Correct answer.
  3. It adds oxygen to the exhaust to help the catalytic converter oxidize hydrocarbons
  4. It increases volumetric efficiency at high engine speed

Explanation

EGR routes a metered amount of exhaust gas back into the intake, which displaces some oxygen and lowers peak combustion temperature. Lower peak temperature suppresses the formation of nitrogen oxides. It is not an oxygen source for the converter, and it does not boost airflow or cool the fuel.

Question 49Engine Systems: Lubrication, Cooling, and Fuel

An engine has a slow coolant leak with no external drips, and the cooling system holds pressure during a static pressure test. Which additional test best confirms a leaking head gasket?

  1. Testing the coolant for combustion gases or checking for bubbles in the radiator with the engine running Correct answer.
  2. Replacing the thermostat and rechecking temperature
  3. Checking the radiator cap with a hand pump
  4. Measuring oil viscosity after a short drive

Explanation

A head gasket leak that lets combustion gas into the cooling system may not show on a static pressure test because the leak opens under combustion pressure. A chemical test for combustion gases in the coolant, or watching for continuous bubbles in the radiator while running, is the appropriate confirmation. The other steps do not detect combustion gas intrusion.

Question 50Engine Systems: Lubrication, Cooling, and Fuel

An engine is filled with oil whose viscosity is far higher than the manufacturer's specification for the prevailing ambient temperatures. Which consequence is most directly expected during a cold start?

  1. Slower oil flow to the bearings and camshaft immediately after startup Correct answer.
  2. Reduced oil film strength at normal operating temperature
  3. Lower oil pressure at hot idle because the oil thins too quickly
  4. Increased aeration of the oil in the sump from the oil pump

Explanation

Viscosity is the oil's resistance to flow, and a grade heavier than specified resists being drawn through the pickup and pumped to distant parts. During a cold start the pump therefore delivers oil to the bearings and camshaft more slowly, which is when most wear occurs. Once warm, a heavier oil generally maintains higher, not lower, pressure.