Automotive Servicing NC III key terms

The set of wearable items such as safety glasses, gloves, coveralls, and steel-toe boots worn to shield the body from workplace hazards. Selection depends on the task, and damaged gear must be replaced before work begins.

The practice of inspecting a work area and task sequence to spot dangers such as rotating parts, hot surfaces, or fuel vapors before work starts. Findings are controlled through elimination, guarding, or procedure changes.

A standardized document supplied with a chemical product that lists its hazards, safe handling, first-aid measures, and spill response. Workers must read it before using an unfamiliar substance and keep it accessible in the shop.

A procedure that isolates energy sources and applies locks and warning tags so equipment cannot be re-energized during service. Each worker applies a personal lock, and removal follows a verified sequence.

Separating used oil, coolant, solvents, batteries, and contaminated rags into labeled containers so each stream can be recycled or disposed of legally. Mixing streams makes recycling impossible and increases disposal cost and liability.

The use of drip trays, absorbent material, and containment berms to stop leaks from spreading and reaching drains or soil. A spill kit should be stocked and workers trained to use it quickly.

The controlled movement of air through a workshop to remove exhaust gas, paint mist, and solvent vapor. Local exhaust at the source is preferred, and carbon monoxide monitors protect workers from odorless exhaust buildup.

A hand tool that applies and signals a precise tightening force so fasteners are neither loose nor stretched. It must be set to the specification, used smoothly, and stored at its lowest setting to keep calibration.

A precision measuring instrument with a calibrated screw that reads outside dimensions to hundredths or thousandths of a millimeter. The spindle and anvil are cleaned before measuring, and the thimble is turned using the ratchet stop.

A measuring tool with a main scale and sliding vernier scale used to read outside, inside, and depth dimensions. The jaws are closed and zero-checked before use, and the tool is read squarely to avoid parallax error.

A set of thin metal blades of known thickness used to check clearances such as valve lash or spark plug gaps. Blades are inserted until a slight drag is felt, and the combined thickness gives the measured clearance.

The allowable range between the largest and smallest acceptable dimension for a part or clearance. A measurement outside tolerance means the part must be adjusted, machined, or replaced according to the service standard.

The tightening force value published by the manufacturer for a specific fastener, often stated with a sequence and a dry or lubricated condition. Applying the wrong value can cause leaks, joint failure, or thread damage.

The comparison of an instrument's reading against a known reference standard to confirm accuracy, followed by adjustment if needed. Measuring tools used for critical work should carry a current calibration record.

The manufacturer's document giving repair procedures, specifications, tightening sequences, and diagnostic steps for a vehicle model. It is the primary authority when a value or procedure is unclear.

A schematic showing electrical circuits with symbols for components, wire colors, connector pins, and power and ground paths. It is used to trace faults and to identify test points without guessing.

Orthographic projections such as front, top, and side views used to describe a part's shape and dimensions on a flat sheet. Understanding the layout prevents misreading hidden features and dimensions.

An alphanumeric code stored by an electronic control unit when a monitored circuit or system falls outside its expected range. The code points to a circuit or system, not automatically to the failed part.

A device that communicates with vehicle control modules to read codes, view live data, and run tests. It reads data the engine computer already knows and does not by itself prove which component has failed.

A snapshot of sensor values and operating conditions recorded at the moment a fault code set. It helps recreate the failure by showing engine speed, load, and temperature when the problem occurred.

A measurement of the voltage lost across a conductor or connection while current flows, revealing resistance problems that a static voltage check would miss. It is performed with the circuit loaded and compared to a limit.

Current that continues to flow from the battery after all accessories are switched off and modules have gone to sleep. Excessive draw flattens the battery overnight and is located by measuring current across each circuit.

A measurement of cylinder pressure during cranking, used to judge piston ring, valve, and head gasket sealing. Results are compared across cylinders, and a wet test helps separate ring wear from valve leakage.

A test in which compressed air is fed into a cylinder at top dead center to measure the percentage of air escaping. Listening at the intake, exhaust, or crankcase identifies where the leak is occurring.

The designed gap between the valve stem and the rocker arm or cam follower. Too little clearance can hold a valve open and burn it, while too much causes noise and reduced lift.

The moment fuel injection begins relative to piston position, which strongly affects power, economy, and emissions. Retarded or advanced timing can cause hard starting, smoke, or knock and must follow the manual.

Adjustment of camber, caster, and toe so the wheels roll in the correct relationship with the road and each other. It is set with the vehicle at ride height and prevents uneven tire wear and pulling.

The shape and location of tread wear, which indicates misalignment, incorrect inflation, or worn suspension parts. Reading the pattern guides diagnosis before any adjustment is made.

The amount a rotating part such as a brake disc or wheel deviates from true rotation. Excessive lateral or radial runout causes vibration and pulsation and is measured with a dial indicator.

Removal of trapped air from the hydraulic brake system by forcing fluid through the lines until no bubbles appear. Air is compressible and causes a spongy pedal and reduced braking force.

A fluid coupling in automatic transmissions that multiplies engine torque at low speed through a stator. It allows the engine to idle while the vehicle is stopped and is often fitted with a lockup clutch.

A condition where the clutch cannot transmit full engine torque, so engine speed rises without matching vehicle speed. Worn friction material, oil contamination, or a misadjusted linkage are common causes.

The ratio between the number of teeth on the ring gear and the pinion gear, which determines how driveshaft speed is converted to wheel speed. It affects acceleration, fuel economy, and speedometer accuracy.

Verification of fluid quantity and condition following the manufacturer's procedure, which often requires a specific temperature and engine state. Wrong fluid or wrong level causes slipping and overheating.

A document authorizing a specific repair, listing the customer's complaint, approved operations, parts, and labor time. It protects both technician and customer by recording exactly what was agreed.

The step of confirming or reproducing the reported problem before any repair, including the conditions under which it occurs. Unverified concerns often lead to unnecessary part replacement and repeat visits.

A documentation format that states what the customer reported, the root cause found through testing, and the action taken. It gives the next technician a complete history instead of a vague description.

A final inspection confirming the repair is complete, fasteners are torqued, fluids are correct, and the original concern is gone. It is performed before the vehicle is returned to the customer.

A controlled drive used to verify a complaint, gather operating data, and confirm the repair afterward. It is done with a valid license, following traffic law, and with a planned route and test points.