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Motor Vehicle Mechanics study materials
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Motor Vehicle Mechanics practice questions

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Question 1Motor Vehicle Mechanics

A four-stroke engine completes one full power cycle in how many crankshaft revolutions?

  1. One revolution
  2. Half a revolution
  3. Two revolutions Correct answer.
  4. Four revolutions

Explanation

In a four-stroke cycle the piston makes four strokes (intake, compression, power, exhaust), which requires two complete turns of the crankshaft. The camshaft turns once in that time, at half crankshaft speed.

Question 2Motor Vehicle Mechanics

Which component opens and closes the poppet valves in time with the crankshaft on a pushrod OHV engine?

  1. The oil pump drive gear
  2. The crankshaft counterweights
  3. The camshaft acting through lifters, pushrods and rockers Correct answer.
  4. The exhaust manifold

Explanation

The camshaft carries lobes ground to the valve timing and transfers motion through lifters, pushrods and rocker arms to the valve stems. Its rotation is synchronized to the crankshaft by the timing chain or belt.

Question 3Motor Vehicle Mechanics

What is the main purpose of the thermostat in an engine cooling system?

  1. To remove dissolved air from the coolant
  2. To pressurize the cooling system above atmospheric pressure
  3. To drive the water pump impeller
  4. To regulate coolant flow so the engine reaches and holds operating temperature Correct answer.

Explanation

The thermostat is a wax-pellet valve that stays closed while the coolant is cold, allowing quick warm-up, then opens to route coolant through the radiator. This keeps the engine within its designed temperature band.

Question 4Motor Vehicle Mechanics

On a manual transmission, what does the clutch friction disc do when the pedal is fully released?

  1. It spins freely with no contact on the flywheel
  2. It locks the input shaft to the gearbox casing
  3. It is clamped between the flywheel and pressure plate and transmits torque Correct answer.
  4. It disconnects the gearbox from the differential

Explanation

With the pedal released, the pressure plate springs clamp the friction disc against the flywheel so engine torque passes to the gearbox input shaft. Depressing the pedal releases that clamp and interrupts the drive.

Question 5Motor Vehicle Mechanics

A tyre is marked 205/55 R16. What does the 55 represent?

  1. Speed rating
  2. Rim diameter in inches
  3. Load index
  4. Aspect ratio: sidewall height as a percentage of section width Correct answer.

Explanation

The second number in a metric tyre size is the aspect ratio, expressing sidewall height as a percentage of the 205 mm section width. Here the sidewall is about 113 mm tall.

Question 6Motor Vehicle Mechanics

What does a reading of 12.6 volts across the battery terminals on a rested, engine-off battery indicate?

  1. A healthy, fully charged 12 V lead-acid battery Correct answer.
  2. A failed alternator diode
  3. A shorted starter solenoid
  4. A battery that is being overcharged

Explanation

A rested lead-acid battery with six cells reads about 2.1 V per cell, giving roughly 12.6 V at full charge. Lower values suggest discharge or a failing cell.

Question 7Motor Vehicle Mechanics

Which tool is correct for measuring the diameter of a valve stem to check wear against specification?

  1. A torque wrench
  2. A feeler gauge
  3. A micrometer Correct answer.
  4. A compression tester

Explanation

A micrometer gives a direct precision measurement of a cylindrical part such as a valve stem. Comparing the result with the service limit shows whether the stem is worn.

Question 8Motor Vehicle Mechanics

In a hydraulic braking system, what happens when the brake pedal is pressed?

  1. The ABS pump alone applies the pads
  2. The brake fluid is drained back to the reservoir to apply force
  3. Air is drawn into the caliper to apply the pads
  4. The master cylinder pressurizes fluid, which pushes the caliper pistons outward Correct answer.

Explanation

Pedal force moves the master cylinder piston, pressurizing an essentially incompressible fluid. That pressure acts on the caliper pistons, which press the pads against the disc.

Question 9Motor Vehicle Mechanics

An engine has low compression on one cylinder and a wet oil test raises the reading noticeably. What does this most likely indicate?

  1. Incorrect valve timing
  2. A burned exhaust valve
  3. Worn piston rings or cylinder bore Correct answer.
  4. A leaking head gasket between cylinders

Explanation

Adding oil temporarily seals the ring-to-bore gap, so a compression rise on the wet test points to ring or bore wear. Valve or gasket faults usually do not improve with oil.

Question 10Motor Vehicle Mechanics

A vehicle pulls steadily to the right on a straight, level road with correct tyre pressures. Which cause best fits?

  1. Low tyre tread depth on both front tyres
  2. Excessive total toe-in on both wheels
  3. Unequal camber or caster between the two sides of the front axle Correct answer.
  4. Too much positive caster on both sides equally

Explanation

A pull to one side means the left and right sides are producing different forces, so an unequal alignment angle such as camber or caster is the likely cause. Symmetrical settings affect both wheels equally and do not cause a directional pull.

Question 11Motor Vehicle Mechanics

Why is a timing belt replacement interval specified in both distance and time?

  1. Rubber degrades with age as well as with running cycles Correct answer.
  2. The tensioner only wears while the vehicle is stationary
  3. Belt life depends only on the number of cold starts
  4. The belt stretches only when the engine is cold

Explanation

Elastomer belts lose strength through heat, ozone and flexing cycles, so a low-mileage vehicle can still have an aged belt. Manufacturers therefore specify whichever limit, distance or time, is reached first.

Question 12Motor Vehicle Mechanics

A diesel engine cranks but will not start, and the glow plug circuit is found open. What is the most direct effect?

  1. The starter motor will not turn
  2. No fuel delivered to the injectors
  3. Poor cold-start combustion because the charge is not preheated Correct answer.
  4. The alternator will not charge

Explanation

Glow plugs warm the combustion chamber air so diesel ignites reliably from compression when cold. An open circuit leaves the charge cold, causing hard or failed cold starting.

Question 13Motor Vehicle Mechanics

During a charging-system test the battery voltage stays near 12.2 V with the engine at 2000 rpm and loads off. What is the most likely fault?

  1. The starter is drawing current continuously
  2. The ignition timing is retarded
  3. The alternator is not charging Correct answer.
  4. The battery is overcharged

Explanation

A working alternator should raise system voltage to roughly 13.8 to 14.5 V at speed. Staying near the rested battery voltage indicates no charging output, so the alternator, its regulator or the field circuit should be checked.

Question 14Motor Vehicle Mechanics

A disc brake squeals only at low speed and the pads show plenty of lining. What is the most appropriate first check?

  1. Machine the disc below minimum thickness
  2. Fit anti-squeal shims or compound and check pad-to-caliper fit Correct answer.
  3. Replace the brake master cylinder
  4. Replace the ABS hydraulic unit

Explanation

Low-speed squeal with serviceable pads is usually high-frequency vibration between pad and caliper. Correct shims, lubricant on the correct contact points and proper fit damp that vibration.

Question 15Motor Vehicle Mechanics

What is the function of the differential in a rear-wheel-drive axle?

  1. To convert rotary motion to linear motion
  2. To multiply engine torque before the gearbox
  3. To let the driven wheels turn at different speeds while transmitting torque Correct answer.
  4. To lock both halfshafts together at all times

Explanation

When cornering, the outer wheel travels a longer path than the inner one, so the differential allows a speed difference while still delivering drive to both wheels. It also provides the final drive ratio.

Question 16Motor Vehicle Mechanics

An engine overheats only at highway speed while idling temperature is normal. Which fault fits best?

  1. A restricted radiator or blocked airflow through the core Correct answer.
  2. A faulty radiator cap releasing at low pressure
  3. A slipping water pump belt at idle only
  4. A thermostat stuck open

Explanation

At speed the engine produces more heat that must be shed by the radiator, so a partly blocked core or obstructed airflow shows up as high-speed overheating. At idle the heat load is lower and the fan can cope.

Question 17Motor Vehicle Mechanics

A spark plug from one cylinder shows heavy black soot with a dry, fluffy deposit. What does this most suggest?

  1. Coolant entering the cylinder
  2. Severe pre-ignition
  3. Correct combustion with normal wear
  4. A rich mixture or weak ignition in that cylinder Correct answer.

Explanation

Dry black carbon fouling indicates unburned fuel depositing as soot, typically from an over-rich mixture or a spark too weak to burn the charge. Coolant contamination gives a different, wet or crusty appearance.

Question 18Motor Vehicle Mechanics

Why must wheel bearings be set to a specified preload or end-float rather than tightened fully?

  1. To keep the hub nut from ever being removed
  2. To increase rolling resistance for better grip
  3. To raise the vehicle ride height
  4. To allow for thermal expansion and retain correct running clearance Correct answer.

Explanation

Bearings need a defined running clearance so heat expansion does not overload the rollers and races. Excess preload causes rapid overheating and failure, while too much play allows wheel wobble.

Question 19Motor Vehicle Mechanics

A scan tool shows a long-term fuel trim of +25 percent on a petrol engine at cruise. What does this indicate?

  1. The fuel injectors are sticking open
  2. The ECU is removing fuel because the mixture is rich
  3. The ECU is adding fuel because the mixture is lean Correct answer.
  4. The oxygen sensor has failed open circuit

Explanation

Positive long-term trim means the control unit is lengthening injector pulse width to correct a lean condition sensed by the oxygen sensor. A large positive value points to unmetered air, low fuel pressure or a weak sensor.

Question 20Motor Vehicle Mechanics

An engine with variable valve timing sets a cam correlation code after a timing belt replacement. What is the most probable cause?

  1. The battery was disconnected during the job
  2. The belt was fitted one tooth out of alignment Correct answer.
  3. The spark plugs were gapped incorrectly
  4. The oil was changed with the wrong grade

Explanation

Cam correlation codes compare camshaft and crankshaft positions, so a belt fitted off by a tooth shifts the cam signal and triggers the code. The timing marks must be rechecked and the belt refitted correctly.

Question 21Motor Vehicle Mechanics

A vehicle with a hydro-pneumatic or conventional ABS has a pedal that pulses and a wheel-speed code for one wheel. Which diagnostic step is most logical first?

  1. Bleed the entire brake system repeatedly
  2. Replace the ABS hydraulic modulator
  3. Replace all four wheel-speed sensors
  4. Inspect that wheel's sensor, tone ring and wiring for damage or debris Correct answer.

Explanation

A single-wheel speed code most often comes from that corner's sensor, tone ring or harness, such as a cracked ring or metallic debris. Confirming the signal at that wheel before replacing expensive hydraulic parts follows sound diagnostic order.

Question 22Motor Vehicle Mechanics

A turbocharged diesel loses power and emits black smoke under load, with a whistle that has become louder. What is the most likely fault?

  1. A boost leak from a split charge-air hose Correct answer.
  2. A blocked exhaust gas recirculation cooler
  3. A worn clutch release bearing
  4. A failed coolant thermostat

Explanation

A split charge-air hose lets pressurized air escape, so less air reaches the cylinders and the mixture over-fuels, giving black smoke and lost power. The escaping air also produces a louder whistle.

Question 23Motor Vehicle Mechanics

After a cylinder head is refitted, the engine overheats and the coolant reservoir bubbles continuously. Which cause should be investigated first?

  1. A thermostat installed the wrong way round
  2. A faulty radiator fan relay
  3. Combustion gas leaking past the head gasket into the cooling system Correct answer.
  4. An over-tightened accessory belt

Explanation

Continuous bubbling with overheating after head work points to combustion gas entering the coolant, typically from a gasket seal or head flatness problem. A chemical block test confirms combustion gases in the coolant.

Question 24Motor Vehicle Mechanics

Why is a torque-to-yield head bolt usually replaced rather than reused?

  1. It must be matched to the gasket thickness
  2. It is made of a softer grade than ordinary bolts
  3. It has been stretched past its elastic limit and will not clamp reliably again Correct answer.
  4. It loses its thread pitch during tightening

Explanation

Torque-to-yield bolts are tightened into the plastic region, so they permanently elongate and lose clamping force if reused. New bolts are specified to ensure even, lasting gasket sealing.

Question 25Motor Vehicle Mechanics

What does an engine oil viscosity grade such as 5W-30 indicate?

  1. The oil's total base number
  2. Cold-temperature flow behaviour and high-temperature viscosity class Correct answer.
  3. The recommended oil change interval
  4. The oil's flash point

Explanation

The W number rates cold cranking and pumping behaviour, while the second number is the kinematic viscosity at 100 degrees Celsius. Together they describe how the oil behaves cold and hot.

Question 26Motor Vehicle Mechanics

A four-cylinder engine has a firing order of 1-3-4-2. If cylinder 1 is at top dead centre on the start of its power stroke, which cylinder is next to fire?

  1. Cylinder 2
  2. Cylinder 3 Correct answer.
  3. Cylinder 4
  4. Cylinder 1 again

Explanation

The firing order lists the sequence in which cylinders produce a power stroke, so the cylinder after number 1 in the sequence 1-3-4-2 is number 3. The order is fixed by the crankshaft and camshaft design. Cylinder 1 cannot fire again until the full four-stroke cycle has passed through all cylinders.

Question 27Motor Vehicle Mechanics

On a four-stroke petrol engine, during which stroke does the intake valve close?

  1. Just after bottom dead centre at the start of the compression stroke Correct answer.
  2. At the end of the compression stroke
  3. At the start of the exhaust stroke
  4. At the midpoint of the power stroke

Explanation

The intake valve closes shortly after bottom dead centre, once the piston has begun to rise on the compression stroke. This slight delay uses intake charge inertia to improve cylinder filling. Closing earlier would reduce volumetric efficiency at higher engine speeds.

Question 28Motor Vehicle Mechanics

Which property of engine coolant is mainly responsible for raising the boiling point above that of plain water?

  1. Its electrical conductivity
  2. Its colour dye
  3. Its surface tension
  4. Its antifreeze concentration, typically glycol Correct answer.

Explanation

Ethylene or propylene glycol raises the boiling point and lowers the freezing point of the coolant mixture. The pressure cap then raises the boiling point further. Dye, conductivity and surface tension do not meaningfully change the boiling point.

Question 29Motor Vehicle Mechanics

A mechanic uses a feeler gauge to check valve clearance on a solid-lifter engine. What is being measured?

  1. The installed height of the valve spring
  2. The thickness of the valve head margin
  3. The gap between the valve stem tip and the rocker or cam follower Correct answer.
  4. The clearance between the valve stem and the guide

Explanation

Valve clearance is the gap in the valvetrain between the cam or rocker and the valve stem tip. It must be set so the valve fully seats when the engine is hot. Too little clearance can hold a valve open; too much causes noise and lost lift.

Question 30Motor Vehicle Mechanics

In a manual gearbox, what is the purpose of the synchroniser assembly?

  1. To provide a direct mechanical drive in top gear
  2. To match the speed of the input gear to the output shaft before engagement Correct answer.
  3. To multiply engine torque at low road speed
  4. To lock the gearbox in neutral during coasting

Explanation

Synchronisers use cone clutches to bring the gear and shaft speeds together before the dog teeth engage. This prevents clashing and allows smooth shifts without double-clutching. They do not change torque multiplication or provide direct drive.

Question 31Motor Vehicle Mechanics

What is the main function of the brake master cylinder reservoir?

  1. To store hydraulic fluid and allow for level changes as the pads wear Correct answer.
  2. To pressurise the fluid before it reaches the calipers
  3. To separate air from the fluid automatically
  4. To cool the brake fluid during heavy use

Explanation

The reservoir holds the hydraulic fluid supply and provides headroom for the level to drop as the pads and discs wear. It also allows for expansion with temperature. It does not generate pressure itself.

Question 32Motor Vehicle Mechanics

A tyre sidewall marking reads 205/55 R16 91V. What does the 55 represent?

  1. The load index of the tyre
  2. The rim diameter in inches
  3. The aspect ratio, the sidewall height as a percentage of the section width Correct answer.
  4. The maximum speed rating in km/h

Explanation

The second number is the aspect ratio, expressing sidewall height as a percentage of the nominal section width. Here the sidewall is 55 percent of 205 mm. The 91 is the load index and V is the speed rating.

Question 33Motor Vehicle Mechanics

Why is a cooling system pressure-tested with the engine off and cold?

  1. To prevent the thermostat from opening
  2. To avoid scalding from hot coolant and to locate leaks safely Correct answer.
  3. To increase the pressure reading
  4. To make the pressure cap open sooner

Explanation

Pressure testing a cold engine protects the technician from burns and pressurised steam. It also gives a stable reading while leaks are traced. A hot system can spray coolant when the tester is connected.

Question 34Motor Vehicle Mechanics

A starter motor spins freely but the engine does not crank. Which component is most likely faulty?

  1. The drive pinion or one-way clutch Correct answer.
  2. The starter solenoid contacts
  3. The battery earth strap
  4. The ignition switch feed to the solenoid

Explanation

If the motor spins but does not turn the engine, the drive pinion is not engaging the flywheel ring gear or the one-way clutch is slipping. The electrical circuit is working because the motor runs. The fault lies in the mechanical drive.

Question 35Motor Vehicle Mechanics

During a compression test on a warm petrol engine, one cylinder reads 40 percent below the others. Adding a few drops of oil raises it only slightly. What does this most suggest?

  1. A leaking intake valve Correct answer.
  2. Excessive carbon build-up on the piston crown
  3. Worn piston rings
  4. A blown head gasket between two cylinders

Explanation

A wet test that does not significantly raise compression points to a leak above the piston, such as a valve or head gasket. Ring wear would usually be sealed by the oil and raise the reading. A valve leak is not sealed by oil added to the cylinder.

Question 36Motor Vehicle Mechanics

An engine has a misfire at idle that clears at higher speed, and a vacuum gauge needle flickers rapidly. What is the most likely cause?

  1. A weak ignition coil at high load
  2. A leaking intake manifold gasket
  3. A restricted fuel filter
  4. A sticking or burned intake valve Correct answer.

Explanation

A rapid vacuum needle flicker with an idle misfire points to a valve that is not sealing consistently, such as a burned or sticking intake valve. The leak becomes less significant as speed rises. A manifold leak would give a steady low reading, not a flicker.

Question 37Motor Vehicle Mechanics

What is the effect of a stuck-open exhaust gas recirculation valve on a warm petrol engine at idle?

  1. Increased turbocharger boost
  2. Reduced NOx and smoother idle
  3. Rough idle and possible stalling due to excessive exhaust gas in the intake Correct answer.
  4. Higher idle speed and lean cruise mixture

Explanation

An EGR valve stuck open lets exhaust gas into the intake at idle, when the engine needs a rich, stable mixture. The result is a rough or stalling idle. EGR should be closed at idle and light load.

Question 38Motor Vehicle Mechanics

A vehicle with a manual gearbox jumps out of third gear under acceleration. Which cause fits best?

  1. A slipping clutch
  2. Worn synchroniser cones
  3. A broken or worn detent spring and selector mechanism Correct answer.
  4. Low gearbox oil level

Explanation

Jumping out of gear under load usually indicates worn detents, a weak spring or selector fork wear allowing the gear to disengage. Synchroniser wear causes grating on engagement, not jumping out. Oil level and clutch slip do not directly cause the gear to pop out.

Question 39Motor Vehicle Mechanics

Which alignment angle describes the tilt of the steering axis when viewed from the front of the vehicle?

  1. Toe
  2. Thrust angle
  3. Camber Correct answer.
  4. Caster

Explanation

Camber is the inward or outward tilt of the wheel from vertical when viewed from the front. Caster is the tilt of the steering axis viewed from the side. Toe is the difference in track between front and rear of the wheels.

Question 40Motor Vehicle Mechanics

A diesel engine produces white smoke continuously after a cold start and the coolant level drops slowly. What is the most likely cause?

  1. A faulty glow plug on one cylinder
  2. A restricted air filter
  3. Coolant entering the combustion chamber through a failed head gasket or cracked head Correct answer.
  4. Advanced injection timing

Explanation

Persistent white smoke with coolant loss suggests coolant is being burned in the cylinders, often from a head gasket or cracked casting. White smoke from a cold engine that clears is normal, but continuous smoke plus coolant loss is not. A compression or cooling-system test would confirm.

Question 41Motor Vehicle Mechanics

What does a brake pedal that sinks slowly to the floor when held under steady pressure indicate?

  1. Glazed brake pads
  2. Air in the hydraulic system
  3. An internal leak past the master cylinder seals Correct answer.
  4. A seized caliper piston

Explanation

A pedal that slowly sinks while held indicates fluid is bypassing the master cylinder piston seals internally. This is a hydraulic pressure loss, not a pad friction issue. Air in the system usually gives a spongy pedal, not a steady sink.

Question 42Motor Vehicle Mechanics

In a vehicle with a conventional alternator, what does the warning lamp staying lit with the engine running most directly indicate?

  1. The starter solenoid is faulty
  2. The charging system is not producing voltage Correct answer.
  3. The ignition timing is retarded
  4. The battery is fully charged

Explanation

The charge warning lamp is wired to the alternator field circuit and lights when the alternator is not generating. With the engine running it should extinguish once output rises. A lamp that stays lit points to a charging fault.

Question 43Motor Vehicle Mechanics

A hydraulic valve lifter ticks loudly when cold and quietens as the engine warms. What is the most likely explanation?

  1. The camshaft lobe is worn flat
  2. The pushrod is bent
  3. The lifter is not holding oil pressure until the oil thins and flow improves Correct answer.
  4. The valve spring is broken

Explanation

Hydraulic lifters rely on oil pressure to maintain zero clearance. Cold, thick oil may not fill the lifter quickly, causing a tick that fades as the engine warms and oil flows. A worn lobe, broken spring or bent pushrod would cause persistent noise and running faults.

Question 44Motor Vehicle Mechanics

A turbocharged engine has low power, blue-grey smoke from the exhaust and excessive oil consumption. Which fault fits best?

  1. Worn turbocharger shaft seals Correct answer.
  2. A blocked intercooler
  3. A faulty wastegate actuator
  4. A restricted exhaust particulate filter

Explanation

Oil entering the intake or exhaust through worn turbo shaft seals burns as blue-grey smoke and raises oil consumption. Power falls because the turbo cannot build boost efficiently. A blocked intercooler or filter causes black smoke and power loss without oil consumption.

Question 45Motor Vehicle Mechanics

Why is a torque wrench calibrated periodically in a workshop?

  1. To reduce the time taken to tighten bolts
  2. To ensure fastener clamp load matches specification and joints do not loosen or fail Correct answer.
  3. To increase the maximum torque it can apply
  4. To allow it to be used as a breaker bar

Explanation

A torque wrench that reads inaccurately will over- or under-tighten fasteners, risking joint failure or stripped threads. Calibration verifies the indicated value against a known standard. It does not change the tool's range or intended use.

Question 46Motor Vehicle Mechanics

A vehicle with independent rear suspension has excessive rear tyre wear on the inner edges of both tyres. Which alignment fault fits best?

  1. A worn steering rack
  2. Excessive negative camber or toe-out on the rear axle Correct answer.
  3. Incorrect front toe-in
  4. Too much positive caster

Explanation

Inner-edge tyre wear on both rear tyres points to excessive negative camber or rear toe-out. These angles are set on the rear axle of an independent suspension. Caster and front toe affect the front tyres and steering feel, not rear inner edges.

Question 47Motor Vehicle Mechanics

An engine is fitted with a mass airflow sensor and a manifold absolute pressure sensor. During diagnosis, the MAF reads low while the MAP reads normal at idle. What is the most useful next step?

  1. Increase the idle speed
  2. Compare MAF and MAP readings against expected values and check for intake leaks or a dirty MAF element Correct answer.
  3. Replace the MAP sensor
  4. Replace the throttle body

Explanation

Two sensors measuring related quantities should agree with expected values. A low MAF reading with a normal MAP suggests an intake leak, a dirty sensing element or a wiring fault. Comparing live data and inspecting the intake path is the logical next step before replacing parts.

Question 48Motor Vehicle Mechanics

A vehicle has a vibration that is felt through the steering wheel and increases with road speed, disappearing when the vehicle is jacked up and the wheels spin freely. What is the most likely cause?

  1. An out-of-balance wheel and tyre assembly Correct answer.
  2. A worn constant-velocity joint
  3. A faulty wheel bearing
  4. An unbalanced driveshaft

Explanation

A speed-related vibration that disappears when the wheels are unloaded is typical of wheel and tyre imbalance. The imbalance is only felt when the tyre is loaded against the road. Driveline and bearing faults usually persist or change with load in other ways.

Question 49Motor Vehicle Mechanics

A technician is diagnosing an intermittent no-start. The engine cranks normally, spark is present, and fuel pressure is within specification, but the injectors do not pulse. Which signal is most critical to check next?

  1. Battery voltage at the starter
  2. Fuel pump relay output
  3. Crankshaft position sensor signal to the engine control unit Correct answer.
  4. Ignition coil primary resistance

Explanation

Injector pulse is triggered by the ECU using crankshaft position information. If spark and fuel pressure are present but injectors do not fire, the ECU may not be receiving a valid crank signal. Checking the sensor signal with an oscilloscope is the logical next step.

Question 50Motor Vehicle Mechanics

During a road test, a vehicle with a locking differential engages abruptly on tight corners. What is the most likely consequence if the fault is ignored?

  1. Improved traction on all surfaces
  2. Lower fuel consumption
  3. Reduced brake wear
  4. Increased tyre scrub and driveline wind-up, leading to component wear Correct answer.

Explanation

A differential that stays locked on tight corners forces the tyres to scrub and loads the driveline with wind-up. Over time this accelerates tyre, halfshaft and differential wear. It does not improve normal road behaviour.