# Car terms, explained

Short, plain definitions of the words mechanics, scanners and owner's manuals use.

## 25 terms

| Term | Meaning |
| --- | --- |
| [ABS](/glossary/abs) | ABS, or anti-lock braking system, stops the wheels from locking up during hard braking so you can keep steering. |
| [All-wheel drive](/glossary/all-wheel-drive) | All-wheel drive (AWD) is a drivetrain that can send engine power to all four wheels automatically to improve traction. |
| [Alternator](/glossary/alternator) | The alternator is an engine-driven generator that powers the car's electrical system and recharges the battery while the engine runs. |
| [Brake rotor](/glossary/brake-rotor) | A brake rotor is the metal disc attached to each wheel that the brake pads clamp onto to slow the car. |
| [Catalytic converter](/glossary/catalytic-converter) | A catalytic converter is a part in the exhaust that uses precious metals to turn harmful engine gases into less harmful ones. |
| [Check engine light](/glossary/check-engine-light) | The check engine light is a dashboard warning that the car's computer has found a problem with the engine, transmission or emissions system. |
| [Coolant](/glossary/coolant) | Coolant, also called antifreeze, is the fluid that carries heat away from the engine and protects it from freezing, boiling and corrosion. |
| [CV axle](/glossary/cv-axle) | A CV axle is a drive shaft with flexible constant-velocity joints that sends engine power to the wheels while they steer and move with the suspension. |
| [CVT](/glossary/cvt) | A CVT, or continuously variable transmission, is an automatic transmission that changes its ratio smoothly instead of shifting between fixed gears. |
| [DTC](/glossary/dtc) | A DTC, or diagnostic trouble code, is a short code the car's computer stores to describe a problem it has detected. |
| [EGR valve](/glossary/egr-valve) | An EGR (exhaust gas recirculation) valve lets a small amount of exhaust back into the engine to lower combustion temperature and reduce emissions. |
| [EVAP system](/glossary/evap-system) | The EVAP (evaporative emission control) system captures fuel vapor from the gas tank and sends it to the engine to be burned. |
| [Fuel trim](/glossary/fuel-trim) | Fuel trim is the correction the engine computer makes to the amount of fuel it injects, based on oxygen sensor readings. |
| [Horsepower](/glossary/horsepower) | Horsepower is a measure of how quickly an engine or motor can do work, which affects acceleration and top speed. |
| [Hybrid car](/glossary/hybrid-car) | A hybrid car combines a gasoline engine with one or more electric motors and a battery to use less fuel. |
| [Limp mode](/glossary/limp-mode) | Limp mode is a protective mode that limits engine power, speed or gears when the car's computer detects a serious problem. |
| [Mass air flow sensor](/glossary/mass-air-flow-sensor) | A mass air flow (MAF) sensor measures how much air is entering the engine so the computer can match the right amount of fuel. |
| [Misfire](/glossary/misfire) | A misfire happens when one or more cylinders do not burn their air and fuel properly, so the engine loses power and runs roughly. |
| [OBD-II](/glossary/obd-ii) | OBD-II is the on-board diagnostic system that monitors a car's engine and emissions parts and stores trouble codes when it finds a problem. |
| [Oxygen sensor](/glossary/oxygen-sensor) | An oxygen sensor, or O2 sensor, measures how much oxygen is in the exhaust so the engine computer can keep the fuel mixture right. |
| [Serpentine belt](/glossary/serpentine-belt) | A serpentine belt is a long, ribbed rubber belt on the front of the engine that powers accessories such as the alternator and AC compressor. |
| [Timing belt](/glossary/timing-belt) | A timing belt is a toothed rubber belt that keeps the engine's crankshaft and camshafts turning in sync. |
| [Torque](/glossary/torque) | Torque is the twisting force an engine or electric motor produces, which is what gets a car moving and helps it accelerate and tow. |
| [TPMS](/glossary/tpms) | TPMS, or tire pressure monitoring system, warns the driver when one or more tires are significantly underinflated. |
| [Traction control](/glossary/traction-control) | Traction control is a system that limits wheelspin when you accelerate by cutting engine power or braking the spinning wheel. |

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Source page: https://diagxcar.com/glossary
General information, not a substitute for a qualified mechanic.