Free Red Seal Automotive Exam Flashcards

Class B for flammable liquids (fuel) and Class C for energized electrical equipment; a multipurpose ABC extinguisher covers ordinary combustibles, flammable liquids, and electrical fires in one unit.

0.001 inch (or 0.01 mm on a metric micrometer) — used to measure shaft diameters, bearing clearances, and cylinder bore wear more precisely than a caliper allows.

To isolate and physically lock out hazardous energy sources (electrical, hydraulic, high-voltage) during service so equipment cannot be energized, started, or moved unexpectedly while a technician is exposed to the hazard.

To visually communicate a controlled product's specific hazard class at a glance (e.g., flame = flammable, corrosion = corrosive, skull and crossbones = acute toxicity), aligned with the Globally Harmonized System (GHS).

Intake (piston down, intake valve open), Compression (piston up, valves closed), Power (spark ignites the mixture, piston driven down), Exhaust (piston up, exhaust valve open) — two crankshaft revolutions per full cycle.

5W is the cold-temperature (winter) viscosity rating — a lower number flows better when cold; 30 is the viscosity grade at 100°C operating temperature. Together they describe a multi-grade oil's flow across a temperature range.

Around 195°F (90°C). The thermostat stays closed below this so the engine reaches operating temperature quickly, then opens to route coolant through the radiator.

Each added pound per square inch (psi) of system pressure raises the coolant's boiling point by roughly 3°F. A 50/50 coolant mix boiling near 220°F under a 15 psi cap will not boil until about 265°F.

The ratio of cylinder volume with the piston at bottom dead center to the volume with the piston at top dead center. Higher compression ratios improve thermal efficiency but require higher-octane fuel to resist detonation.

14.7:1 by mass (14.7 parts air to 1 part fuel) — the theoretically ideal ratio for complete combustion, and the target the PCM uses for closed-loop fuel control.

Simultaneously oxidizes carbon monoxide (CO) and unburned hydrocarbons (HC) into CO2 and water, and reduces nitrogen oxides (NOx) into nitrogen and oxygen.

Recirculates a metered amount of exhaust gas into the intake to lower peak combustion temperature, which reduces the formation of NOx emissions.

Fuel vapors escaping to the atmosphere. Vapors are captured in a charcoal canister and later purged into the intake to be burned, controlled by purge and vent solenoid valves.

Voltage equals current multiplied by resistance: V = I x R. Used to solve for any one value in a circuit when the other two are known.

P = V x I (Power = Voltage x Current), measured in watts.

Current is the same at every point in the circuit; voltage divides across each load in proportion to its resistance, and total resistance equals the sum of all resistances.

Voltage is the same across every branch; current divides among branches in inverse proportion to resistance, and total resistance is always less than the smallest branch resistance.

An open-circuit voltage of about 12.6V and an electrolyte specific gravity of about 1.265 (at 80°F/26.7°C).

Apply a load equal to half the battery's Cold Cranking Amps (CCA) rating for 15 seconds; the battery passes if voltage stays at or above 9.6V at 70°F (21°C).

Approximately 13.5-14.5V. The voltage regulator holds output in this range to charge the battery and supply electrical loads without overcharging.

It measures resistance in a live circuit by reading the voltage lost across a wire, connector, or ground under load. A healthy connection typically drops well under a few tenths of a volt; excessive drop points to corrosion or a poor connection.

Roughly 25-50 milliamps (0.025-0.05A), though it varies by vehicle and module count. Excess draw can discharge the battery over several days of non-use and points to a module failing to sleep.

About 60 ohms. Two 120-ohm terminating resistors sit at opposite ends of the twisted-pair bus and are wired in parallel, combining to 60 ohms; a reading of 120 ohms means one end's resistor is missing.

Temporarily disconnects engine torque from the transmission input shaft so gears can be selected without grinding, using a friction disc clamped between the flywheel and pressure plate.

Uses friction cones to match the speed of a gear to the speed of the shaft before the dog teeth/collar engage, allowing smooth, quiet gear changes without clashing.

A fluid coupling (impeller, turbine, stator) that transmits and multiplies engine torque to an automatic transmission at low speed. The lock-up clutch mechanically locks the impeller to the turbine at cruise speed to eliminate fluid slip and improve efficiency.

The sun gear (center), the planet gears/carrier (orbit the sun gear), and the ring gear (outer internally-toothed gear). Holding or driving different members produces different ratios, including overdrive and reverse.

A steel belt or chain rides between two variable-diameter pulleys; changing the effective pulley diameters produces an infinitely variable ratio instead of fixed gear steps.

It allows the outer wheel to turn faster than the inner wheel while cornering, splitting torque equally to both wheels. Its limitation: if one wheel loses traction, all engine torque routes to that wheel, which can leave the vehicle stuck.

Spring-loaded clutch packs resist speed differences between the axle shafts, transferring more torque to the wheel with better traction instead of letting a spinning wheel take all the torque.

Transmits power at a constant rotational velocity through a wide range of steering and suspension angles, without the speed fluctuation a simple U-joint would introduce at large operating angles.

Pascal's Law: pressure applied to an enclosed, incompressible fluid transmits equally in all directions. Because caliper/wheel-cylinder piston area is larger than the master cylinder piston, the same pressure produces greater clamping force at the wheel.

DOT 3: about 205°C (401°F). DOT 4: about 230°C (446°F). DOT 5.1: about 260°C (500°F) or higher. All three are glycol-based and hygroscopic (absorb moisture over time), which lowers the 'wet' boiling point.

A passive (variable-reluctance) sensor uses a magnet and coil to generate an analog AC signal from a toothed ring. An active sensor uses a powered Hall-effect or magnetoresistive element with a digital output, and reads accurately down to very low or zero speed.

Works with ABS to vary front-to-rear brake force based on vehicle load and weight transfer during braking, improving stability and shortening stopping distance compared to a fixed mechanical proportioning valve alone.

Bleed the wheel farthest from the master cylinder first and work toward the closest — typically right-rear, left-front, left-rear, right-front — to purge air from the longest lines first.

The inward/outward tilt of the top of the tire from vertical, viewed from the front. Positive camber tilts the top of the wheel outward; excessive camber in either direction causes uneven wear on one edge of the tread.

The forward/rearward tilt of the steering axis viewed from the side. Positive caster (top of the steering axis tilted rearward) improves straight-line stability and steering wheel self-centering, but does not directly cause tire wear.

The difference in distance between the leading and trailing edges of the tires, viewed from above. Toe-in means the leading edges are closer together; toe-out means they are farther apart. Incorrect toe causes rapid feathered/sawtooth tire wear.

The angle between the rear axle's actual direction of travel (thrust line) and the vehicle's geometric centerline. An incorrect thrust angle causes the vehicle to 'dog-track' and can make it impossible to align front toe to a straight steering wheel.

When a tire's pressure falls 25% or more below the vehicle manufacturer's recommended cold placard pressure, per FMVSS/CMVSS 138.

Compression (compressor raises pressure and temperature of refrigerant gas), Condensation (condenser rejects heat, refrigerant becomes a high-pressure liquid), Expansion (metering device drops pressure so refrigerant cools), Evaporation (evaporator absorbs cabin heat, refrigerant boils back to a low-pressure gas).

R-1234yf. It has a much lower Global Warming Potential (under 1, versus about 1,430 for R-134a) but is mildly flammable (A2L classification), requiring dedicated recovery/recycle/recharge equipment and service procedures.

It meters (restricts) refrigerant flow between the high side and low side, creating a sharp pressure drop so liquid refrigerant can expand and cool before entering the evaporator.

An actuator-controlled door that mixes heated air from the heater core with cooled/unheated air in proportions to reach the temperature selected by the driver or ATC module.

Refrigerants such as R-134a and R-1234yf are regulated ozone- and climate-impacting substances; venting is illegal and environmentally harmful, so recovery machines capture, filter, and store refrigerant for recycling or proper disposal.

P = Powertrain (engine/transmission), B = Body, C = Chassis, U = Network/communication — U-codes indicate module or bus communication faults.

P0300 indicates a random or multiple-cylinder misfire not tied to one cylinder. P0301 (and P0302, P0303, and so on) indicates a misfire detected on that specific numbered cylinder.

A snapshot of key sensor values (RPM, load, coolant temperature, fuel trim, vehicle speed, and more) captured by the PCM at the exact moment a fault was first detected, helping a technician recreate the conditions that caused the code.

Verify the customer's concern is actually present and gather information — related codes, freeze frame data, and technical service bulletins — before performing component-level tests, so the technician does not waste time chasing the wrong system.