SVP Light Vehicle Mechanic cheat sheet

A vehicle supported only by a hydraulic jack is unstable; axle stands rated above the lifted load must carry the vehicle before any person goes underneath.

Wheel chocks are placed against the wheels remaining on the ground, on both the front and rear sides of each chocked wheel, before lifting.

Lead-acid battery charging can release hydrogen gas, which is explosive between roughly 4% and 75% concentration in air; charging areas require ventilation.

Brake fluid is hygroscopic and attacks painted surfaces; spills are flushed with water and absorbed rather than wiped with a dry rag.

Petrol vapour is heavier than air and collects in pits and low floor areas; ignition sources are excluded from those zones.

Fire classes are A for ordinary combustibles, B for flammable liquids, and C for energized electrical equipment; CO2 and dry powder suit live electrical equipment.

Engine exhaust contains carbon monoxide; exhaust extraction is connected whenever an engine runs inside a workshop.

Before welding or grinding, combustible material is removed from a radius of at least 10 m and a fire watch is posted.

Battery removal sequence is negative terminal first; installation sequence is negative terminal last, reducing short-circuit risk from tools.

Torque equals force multiplied by perpendicular distance: T = F × r; 1 N·m equals about 0.7376 lbf·ft.

A click-type torque wrench is stored at its lowest scale setting to preserve spring calibration.

Micrometer reading equals barrel scale plus thimble scale multiplied by least count; a typical metric thimble reads to 0.01 mm.

A common vernier caliper least count is 0.02 mm; the reading is main scale plus the aligned vernier line multiplied by 0.02 mm.

A feeler gauge measures valve clearance and gap; blades must be clean and inserted with light drag, not forced.

A dial indicator on a magnetic base measures shaft runout and end float.

A multimeter measures voltage in parallel and current in series; resistance is never measured on a live circuit.

Tap drill size for a metric coarse thread is approximately major diameter minus thread pitch.

Impact sockets are softer and thicker than chrome hand sockets; chrome sockets can crack or shatter when used on impact tools.

The four-stroke cycle is intake, compression, power, and exhaust; two crankshaft revolutions complete one cycle.

Compression ratio equals swept volume plus clearance volume, divided by clearance volume.

Engine displacement equals π/4 × bore² × stroke × number of cylinders.

Torque-to-yield head bolts are tightened to a torque then an additional angle; they stretch permanently and are replaced, not reused.

Piston ring end gap is measured with a feeler gauge after squaring the ring in its cylinder bore.

Cylinder taper and out-of-round are measured with a bore gauge at multiple heights and in two directions.

Valve clearance is set cold or hot per manufacturer; too little clearance can hold a valve open and reduce compression.

Timing belt alignment marks must match crankshaft and camshaft marks; the engine is rotated twice by hand before starting.

Low oil pressure causes include worn bearings, a weak pump, a stuck relief valve, and oil dilution.

Stoichiometric gasoline combustion is about 14.7:1 air-fuel by mass, corresponding to lambda 1.

The crankshaft position sensor provides engine speed and crank position; the camshaft position sensor provides cylinder identification and phase.

Closed-loop fuel control uses the upstream oxygen sensor signal to correct fuel delivery.

Positive fuel trim means the ECU is adding fuel because the mixture is lean; negative fuel trim means it is removing fuel from a rich mixture.

A knock sensor detects detonation, and the ECU retards ignition timing in response.

Drive-by-wire throttle systems use accelerator pedal position sensors and throttle position sensors with redundant signals.

A MAP sensor measures manifold absolute pressure or vacuum; a MAF sensor measures intake air mass.

Freeze frame data records operating conditions at the moment a diagnostic trouble code is set.

P0300 indicates random or multiple misfire; P0301 indicates cylinder 1 misfire.

Lambda equals actual air-fuel ratio divided by stoichiometric air-fuel ratio; lambda above 1 is lean and below 1 is rich.

A catalytic converter oxidizes CO and HC and reduces NOx; it requires closed-loop control to operate efficiently.

The EVAP charcoal canister stores fuel vapour, and the purge valve meters that vapour into the intake.

EGR lowers peak combustion temperature and reduces nitrogen oxide formation.

The PCV system recirculates crankcase blow-by gases into the intake for burning.

A diesel particulate filter traps soot; regeneration oxidizes the soot at high exhaust temperature.

Black exhaust smoke indicates over-fuelling or rich mixture; blue smoke indicates oil burning; white smoke indicates coolant or water.

Gasoline direct injection sprays fuel directly into the cylinder at high pressure.

A fuel pressure regulator maintains fuel pressure at a defined value relative to intake manifold pressure.

Ohm's law: V = I × R; power: P = V × I = I² × R.

Series circuits carry the same current and sum voltages; parallel circuits have the same voltage and sum currents.

A 12 V lead-acid battery at rest shows about 12.6 V at 100% state of charge, 12.4 V at about 75%, and 12.2 V at about 50%.

Alternator charging voltage is typically 13.8 V to 14.5 V.

Voltage drop testing is performed with the circuit loaded; excessive drop indicates unwanted resistance.

Parasitic draw is measured with an ammeter in series with the battery; many vehicles should draw below about 50 mA after modules sleep.

A relay has a coil control circuit and separate contact load circuit.

A CAN bus uses a twisted pair; two 120 Ω terminating resistors produce about 60 Ω across the bus.

A diode permits current flow in one direction and is used in the alternator rectifier.

Gear ratio equals driven gear teeth divided by drive gear teeth; torque is multiplied by the ratio.

A manual clutch assembly includes the flywheel, friction disc, pressure plate, and release bearing.

A torque converter multiplies engine torque at stall and contains a lock-up clutch for cruising.

An automatic planetary gearset uses sun, planet, and ring gears; clutches and brakes hold members to select ratios.

A CVT varies pulley diameter and belt or chain position to change ratio continuously.

A differential allows driven wheels to rotate at different speeds during turns while transmitting drive.

ATF level is checked at the specified temperature with the engine running and selector position per the manufacturer's procedure.

A transfer case selects two-wheel drive or four-wheel drive and may include a low-range gear.

Clutch pedal free play prevents the release bearing from carrying a constant load.

Hydraulic pressure equals force divided by piston area; a larger output piston area produces greater force at the same pressure.

DOT 3 and DOT 4 glycol brake fluids are hygroscopic; DOT 5 silicone fluid is not compatible with glycol fluid.

Brake fade is loss of friction from heat; boiling brake fluid produces a spongy pedal and reduced braking.

Disc runout is measured with a dial indicator; excessive runout can cause pedal pulsation.

ABS modulates brake pressure using wheel speed sensors to prevent wheel lock and preserve steering control.

Bleeding usually starts at the wheel farthest from the master cylinder and proceeds to the nearest.

A parking brake may be mechanical or electric and typically acts on the rear brakes.

Minimum brake pad friction material and disc thickness are specified by the manufacturer.

Moisture contamination lowers brake fluid boiling point and increases vapour-lock risk.

Camber is the inward or outward tilt of the top of the wheel viewed from the front; negative camber means the top tilts inward.

Caster is the forward or backward tilt of the steering axis; positive caster improves straight-line stability and self-centering.

Toe is the difference between the front and rear distances across a pair of wheels; toe-in means the fronts are closer together.

A MacPherson strut combines a coil spring and damper with a structural suspension location.

Ball joint play is checked with the wheel unloaded and a lever; vertical play beyond specification requires replacement.

Thrust angle is the average rear toe direction relative to the vehicle centreline.

Underinflation increases rolling resistance and wear on both tire shoulders.

Wheel alignment adjusts camber, caster, and toe to manufacturer specifications.

The A/C cycle consists of compressor, condenser, expansion device, and evaporator.

Refrigerant absorbs heat when evaporating at low pressure and rejects heat when condensing at high pressure.

The high side of an A/C system is at high pressure and high temperature; the low side is at low pressure and low temperature.

R-134a and R-1234yf are not interchangeable; system lubricants and service fittings differ.

Refrigerant must not be vented to atmosphere; it is recovered and recycled.

The pressure-temperature relationship of a refrigerant is used to assess charge and system performance.

The heater core uses engine coolant to warm cabin air.

The blend door controls cabin air temperature by mixing heated and cooled air.

A cabin filter removes dust and pollen from air entering the passenger compartment.

The first character of a DTC identifies the system: P powertrain, C chassis, B body, U network.

Diagnostic sequence is confirm the complaint, scan all modules, perform visual inspection, then test the affected circuit.

Positive long-term fuel trim indicates a lean condition in which the ECU adds fuel.

A compression test is performed with the throttle open and all spark plugs removed; cylinders are compared within specification.

A steady low vacuum gauge reading can indicate an intake leak or worn piston rings.

An oscilloscope displays voltage over time and is used for injector, ignition, and CAN signals.

Freeze frame data shows operating conditions at the moment a DTC was set.

Intermittent faults commonly come from poor connections, chafed wiring, heat, or vibration.

Voltage drop testing locates high-resistance connections and cables.

Many regions set a legal minimum tire tread depth of 1.6 mm; worn tires reduce wet grip and increase hydroplaning risk.

In oil grade 5W-30, the first number indicates cold-flow performance and the second indicates viscosity at operating temperature.

Coolant freeze protection is checked with a hydrometer or refractometer against the climate requirement.

Brake fluid moisture content is tested and fluid replaced at the manufacturer's interval or when contamination is indicated.

Lug nuts are tightened to the specified torque in a star or crossing pattern.

Serpentine belt cracking, glazing, or fraying indicates replacement.

Battery terminals are cleaned and the battery load-tested when state of charge or cranking performance is suspect.

An air filter is inspected for restriction and replaced at the specified interval or when contaminated.

Service intervals are set by the manufacturer according to time, distance, and severe-use conditions.