There are thousands of car parts that make up each vehicle on the road. If you’re new to cars, it can feel pretty overwhelming to learn all the part names and what they do.
This article is intended to help bring you up to speed on how cars work as fast as possible. Here is an alphabetized list of common car part names, along with other common names and short descriptions on what each part does.
How to Use This Guide
Car parts are divided into categories by vehicle system. Check out the Table of Contents to learn more about a specific car part or system.
Anti-Lock Braking System (ABS)
1) ABS Module
The ABS module is a computer that controls brake actuation to individual wheels. It is an integral part of the ABS system that keeps your wheels turning even when you stand on the brake pedal.
A rolling tire has more grip than a sliding tire. The ABS module is also used as part of the traction and stability control systems.
Where It’s Located: In the engine compartment, usually mounted on the firewall or fender.
2) Wheel Speed Sensor (aka ABS Sensor)
Wheel speed sensors detect how fast each individual wheel is spinning, giving crucial data to the anti-lock braking system. Wheel speed sensors are often optical sensors and are found near the wheels.
Some wheel speed sensors are integrated into the hub assembly.
Where It’s Located: On each wheel of a vehicle, usually near the brake rotor or hub assembly.
3) Body Control Module (BCM)
The body control module is a computer that controls the various electronics around the interior of the vehicle. This includes door locks, window switches, heated seats, and sunroof controls.
Where It’s Located: Typically located under the dashboard or behind the glove box.
4) Instrument Cluster
The instrument cluster is the set of gauges behind the steering wheel. Some vehicles have multiple instrument clusters, like the Mini Cooper.
Where It’s Located: On the dashboard of a vehicle, directly in front of the driver.
An odometer tells you how far a vehicle has traveled since it was built. Many governments track mileage on registered vehicles, and the value of a vehicle is directly tied to the number of miles on the clock. It’s important to maintain an accurate odometer reading.
Where It’s Located: In the instrument cluster, near the speedometer and other gauges.
6) Rear Defroster (Rear Defogger)
A rear defroster clears ice and fog from your rear window. Rear defrosters work by heating thin wires that run along the window.
Where It’s Located: On the rear window of a vehicle, typically in a grid of wires.
A speedometer tells you how fast you’re going, either in miles per hour (mph) or kilometers per hour (kph), depending on the country you live in. Older speedometers were cable driven, but modern speedometers are entirely electronic.
Where It’s Located: In the instrument cluster directly in front of the driver.
A tachometer tells you the engine speed in revolutions per minute (RPM). Engine speed is good to know on manual transmissions, because it helps you know when you should change gears. Not all vehicles have a tachometer.
Where It’s Located: Usually in the instrument cluster next to the speedometer.
9) Yaw Sensor
A yaw sensor is an accelerometer tells the ECU how quickly the vehicle is turning. Yaw sensor data is used in the stability control system. Taking the steering angle sensor data into account, the computer can calculate where you’re trying to go and compare this to where the car is actually going.
Where It’s Located: Normally located under the driver or passenger seat, mounted on the level floorboard to access the vehicle’s center of gravity.
10) Lug Bolt
A lug bolt threads through the brake rotor and hub, holding the wheels to the car. Lug bolts are commonly found on European vehicles such as BMW and Audi.
Where It’s Located: On the wheel hubs of a car.
11) Lug Nut
Lug nuts thread onto wheel studs in the hub assembly, holding the wheel to the car. Lug nuts are far more common than lug bolts. They are typically considered to be easier to work with while changing a tire, since you can hang the wheel off the studs during installation.
Some aftermarket companies offer lug nut conversion kits for vehicles that came with lug bolts.
Where It’s Located: On the wheels of a car.
12) Power Steering Pump
A power steering pump provides a hydraulic assist to the driver, reducing steering effort. It is powered by the crankshaft via an accessory belt. Electric power steering systems (EPS) do not use hydraulic fluid.
Where It’s Located: Typically on the front of the engine.
13) Steering Rack
Where It’s Located: Near the front of the car and connected to the steering wheel and the front wheels.
A tire is the literal rubber that meets the road. Tires are the only points of contact between your vehicle and the ground. Tire compounds vary from very sticky for maximum grip to fairly hard for maximum tread life.
Different tread patterns offer different benefits in inclement weather such as rain, ice, or snow. Winter tire compounds are specifically made to handle cold weather conditions.
Where It’s Located: At each corner of a car and mounted on the wheels.
Wheels are what the tires mount to. Made of a strong metal alloy, the wheels allow the tires to bolt to the car.
Where It’s Located: At each corner of a car and attached to the axles.
16) Windshield (Windscreen)
A windshield defends the driver against bugs and debris, while allowing clear visibility of the road ahead. Windshields are designed to be very strong. When they break, they don’t shatter like other windows; they stick together instead.
Where It’s Located: At the front of the car and is positioned between the A-pillars on either side.
17) Wing (Spoiler)
A wing or spoiler provides downforce, increasing load over the tires. This improves cornering grip, but increases drag. A wing with high downforce can lower the top speed of a vehicle. Some factory wings are included for aesthetic purposes, but most do provide some level of downforce at speeds over 100 mph (160 kph).
Where It’s Located: Typically located on the rear of a car, either on the trunk, hatchback, or roof.
18) Brake Caliper
A brake caliper provides the clamping force against the brake pad that slows the vehicle. There are two main brake caliper designs: floating and fixed calipers. Fixed calipers have pistons and bleeder screws on both sides of the caliper and are typically found on performance vehicles.
Where It’s Located: Near each wheel rotor and it’s attached to the suspension or steering knuckle.
19) Brake Drum
Brake drums are found on older drum brake systems. They use internal shoes instead of calipers and brake pads to slow the vehicle.
Where It’s Located: On the inside of a car’s wheels.
20) Brake Fluid
Brake fluid is a hydraulic fluid that transfers the force from the brake pedal to the brake calipers. Brake fluid is hygroscopic, meaning it absorbs moisture from the air over time. The more moisture there is in brake fluid, the lower the boiling point.
If you boil your brake fluid, you won’t be able to stop the car. This is why brake fluid must be changed regularly.
Where It’s Located: Typically in a transparent reservoir near the back of the engine bay on the driver’s side of the car.
21) Brake Line (Brake Hose)
Brake lines connect the master cylinder to the calipers. Many vehicles use multiple brake line circuits. Separate circuits means you’ll still have brakes even if one brake line has a leak in it.
Where It’s Located: Throughout the underside of a car and connect the master cylinder to the brake calipers or wheel cylinders.
22) Brake Master Cylinder
A brake master cylinder houses a piston that compresses brake fluid when you step on the brake pedal. Master cylinders also contain a reservoir of extra fluid. As you use up the brake pads, the brake fluid level drops slightly in the reservoir.
It’s a good idea to check your brake fluid regularly. You won’t be able to stop the car if you run out of brake fluid.
Where It’s Located: Typically on the driver’s side of the engine compartment, near the firewall that separates the engine compartment from the passenger compartment.
23) Brake Pad
A brake pad is the friction material that contacts the rotor. Brake pads slow the vehicle by clamping down on the rotor, providing friction and adhesion forces that turn the kinetic energy of a moving vehicle into heat.
Where It’s Located: Inside each brake caliper and they are pressed against the brake rotor when brakes are applied.
24) Brake Rotor
Brake rotors are iron or steel discs that rotate with the wheels. When you apply the brakes, the brake rotor is slowed, which in turn slows the rest of the vehicle. Some high performance brake rotors are made out of carbon ceramic, but this is typically only found on exotic sports cars.
Where It’s Located: Behind each wheel of a car, and attached to the hub assembly.
25) Parking Brake (E-Brake or Handbrake)
The parking brake applies the brakes to the rear wheels, allowing your vehicle to remain stationary even on steep hills. Some parking brakes use a drum and shoes, but others use a brake caliper.
Many modern parking brakes are electronic and must be put into service mode before you work on the rear brakes.
Where It’s Located: Within the rear wheels of a vehicle.
26) Antifreeze (Coolant or Water)
Coolant is the liquid used in water cooled engines. Typically made of ethylene glycol, antifreeze lowers the freezing point so your coolant won’t freeze, even when it’s very cold outside.
Some people who live in hot climates can run pure deionized water with no antifreeze. If you do live in a hot climate, it’s still a good idea to add a product for lubrication and rust prevention like Water Wetter, though.
Where It’s Located: Typically held in a transparent plastic reservoir near the radiator at the front of the engine bay. The fluid circulates throughout the engine block, cylinder head, and radiator.
27) Coolant Hose
A coolant hose transports coolant to and from the engine block.
Where It’s Located: In the engine bay. The hoses connect the engine block and radiator to the water pump and heater core.
28) Coolant Reservoir (Overflow Reservoir)
A coolant reservoir is an additional container for coolant that is connected to the radiator. As the engine heats up, pressure builds and coolant expands. When radiator pressure exceeds the threshold of the radiator cap, the radiator cap opens to allow this excess pressure to vent.
The overflow reservoir catches this coolant to be used later. As the engine cools, the radiator draws the coolant back from the overflow reservoir to replenish its supply. Your coolant reservoir should have a high and low level mark on it, and the coolant level should be maintained between these lines.
Where It’s Located: Normally near the radiator at the front of the engine bay.
29) Coolant Temperature Sensor
A coolant temperature sensor measures the temperature of coolant in the engine block. This information is typically displayed in the instrument cluster in a temperature gauge.
Where It’s Located: Typically near the thermostat housing or on the engine block.
A radiator cools water in the engine. As you drive, air passes through tiny metal fins. This lowers the temperature of the coolant down to ambient temperature.
Since a vehicle’s operating temperature is around 212 degrees Fahrenheit (100 C), ambient temperatures are sufficient to cool the engine, even on a very hot day.
Where It’s Located: At the front of the car, behind the grille.
31) Radiator Cap
A radiator cap contains the coolant in the radiator. It is equipped with a spring that compresses when the radiator pressure reaches a certain threshold, allowing excess pressure to vent.
Where It’s Located: On top of the radiator.
A thermostat is a mechanical device that regulates the temperature in the engine. When the engine is cold, the thermostat closes to allow coolant to reach operating temperature quickly. Engines run less efficiently when they are cold.
Once the engine temperature heats up enough, the thermostat opens to allow cold coolant to enter the engine. The cycle repeats as needed while you drive.
Where It’s Located: Typically at the engine end of the upper radiator hose.
33) Water Pump
A water pump circulates coolant through the engine block. This allows hot coolant to reach the radiator quickly to keep the engine temperature in check.
Where It’s Located: Normally on the front of the engine, and it’s driven by a belt connected to the crankshaft.
34) Accessory Belt (Serpentine or V-Belt)
An accessory belt connects a component in the engine bay to the crankshaft. As the crankshaft rotates, this rotation delivers power to other devices such as the alternator and A/C compressor.
Where It’s Located: At the front of the engine.
35) Air Filter (Engine)
Engine air filters remove debris from the air that could damage the engine. They are typically made of paper from the factory, although reusable aftermarket filters exist.
Where It’s Located: Typically in a plastic box near the engine’s air intake, which is usually located at the front of the engine bay.
36) Apex Seal
Apex seals separate the three combustion chambers in a rotary engine. They are most commonly found in the 13B rotary engine, although older rotary engines exist as well. Apex seals are analogous to piston rings in a standard piston engine.
Where It’s Located: In a rotary engine, at the tip or “apex” of the triangular rotor inside the engine.
A bearing is a metal surface that allows a component to rotate on one axis with minimal friction. Rod bearings and main bearings allow the connecting rods and crankshaft to rotate inside the engine with minimal friction. Oil is injected inside the bearings to keep the system lubricated.
Where It’s Located: Different types of bearings are located throughout a car such as the engine crankshaft, transmission input/output shafts, and wheel hubs.
38) Belt Tensioner (or Chain Tensioner)
A tensioner applies tension to an accessory belt, timing belt, or timing chain. Releasing tension allows for easy installation and removal. Precise tension is important for timing chains and belts to maintain accurate timing.
An accessory belt that is too loose may squeal. A belt that is too tight may put too much stress on accessory pulleys, and can even cause water pump failure.
Where It’s Located: Typically near the front of the engine.
39) Camshaft (Cam)
A camshaft is a long rod with oblong lobes that open and close the valves. Some vehicles have a single camshaft, others have multiple. Camshafts are timed with the crankshaft, meaning they open and close during a very specific window. This allows air to enter the engine and exhaust to exit after combustion.
Where It’s Located: Inside the engine block, above the crankshaft.
40) Camshaft Lobe
A cam lobe is a teardrop shaped protrusion that lines up with each of the valves. As the camshaft turns, the longer side of the cam lobe pushes the valve open. These lobes are offset based on the engine’s firing order. Cylinders fire at different times to keep the engine balanced and provide smooth power delivery.
Where It’s Located: On the camshaft inside the engine block.
41) Connecting Rod
Connecting rods connect the pistons to the crankshaft. Rods are connected to the crankshaft offset from center, so when the piston pushes down on the rod, the rod will spin the crankshaft.
Where It’s Located: Inside the engine block and each rod connects a piston to the crankshaft.
The crankshaft transfers the up-and-down motion of the pistons to a rotational force used to drive the wheels. Crankshafts live in the middle of the engine and also power all of the vehicle’s accessories in the engine bay using the accessory belt.
Where It’s Located: Inside the engine block, below the cylinders.
43) Cylinder Head
A cylinder head houses the valvetrain: the valves, camshafts, shims, lifters, and rocker arms (where applicable). Cam gears are bolted to the front of the cylinder head which allows a timing chain or timing belt to rotate each camshaft in time with the crankshaft.
Where It’s Located: On top of the engine block.
44) Engine Block
The block is the core of a combustion engine. Often called the “bottom end”, the block houses the crankshaft, pistons, main bearings, rod bearings, and connecting rods. When purchasing an engine, the term “short block” refers to just the engine block, and the term “long block” refers to the block with the cylinder head(s) attached.
Where It’s Located: At the bottom of the engine assembly.
45) Gasket (Seal)
A gasket is a seal between two components that is intended to prevent fluid leakage. Gaskets can be made out of many different materials depending on what type of fluid they are trying to seal. Generally speaking, the term “gasket” is commonly used for a flat metal or paper seal, and “seal” is used to refer to a rubber ring.
Where It’s Located: All around the internal components of the engine, typically between two machined surfaces that are bolted together.
A gear is a toothed wheel that engages with a belt or other gears. Gears may be made of metal, plastic, or polyurethane depending on the application.
Where It’s Located: Inside the transmission, transaxle, and differential(s).
47) Head Gasket
A head gasket is a large gasket that sits between the engine block and the cylinder head. This keeps combustion gases inside the combustion chamber and coolant inside the water jackets of the engine block. It is usually made out of metal.
Where It’s Located: Between the cylinder head and the engine block.
48) Idle Air Control Valve (IAC)
An idle air control valve regulates air when the engine is idling. The ECU uses a sensor on the IAC to determine how much air is needed to allow the vehicle to idle smoothly.
Where It’s Located: Near the throttle body.
49) Oil Pump
An oil pump is the heart of your engine, pumping oil throughout the engine block. Oil lubricates the engine, reducing friction and preventing metal on metal contact.
Where It’s Located: On the front of the engine around the nose of the crankshaft.
A piston is the cylindrical component that moves back and forth inside a reciprocating combustion engine. During the ignition stroke, combustion gases expand and force the piston downward. This force transferred to the connecting rod and then the crankshaft.
Where It’s Located: Deep inside the engine.
51) Piston Ring
Piston rings seal the combustion chamber to maximize efficiency of the combustion stroke. There are several piston rings, each with a different purpose. The compression ring seals the combustion chamber. The oil control ring keeps excess oil off of the cylinder walls.
Where It’s Located: Around the top of each piston.
A pulley is a wheel that is driven by a belt or chain. Pulleys designed to engage with a serpentine belt may have ribs that mesh with the belt. They are used to power components such as the water pump.
Where It’s Located: On the front of the engine. Accessory pulleys are usually visible when you pop the hood. Timing pulleys are typically not visible without removing the timing cover(s).
Vehicles with a single camshaft use pushrods to connect the motion of the cam lobes to the rocker arms. Rocker arms then transfer this motion to the valves. Pushrod systems are found in many V8 engines such as Chevrolet’s LS engine.
Where It’s Located: Inside a single cam V8 engine.
54) Rocker Arms (Rockers)
Rocker arms transfer motion from the pushrod to the valves. They work a little like a seesaw with a pivot point in the middle: when the pushrod moves up, it forces the valve open by pushing the opposite end down. When it’s time for the valve to close, the valve spring pushes up on the opposite side.
Where It’s Located: Inside the head of a pushrod V8 engine.
A sprocket is a gear that is designed to engage with a chain, rather than a gear or a belt. Sprocket teeth are pointier than gear teeth, and sprockets are almost always made of metal.
Where It’s Located: On the front of the engine when a timing chain is used.
A starter is a large electric motor that is powerful enough to turn the engine over. When you turn the key, the starter solenoid triggers the starter motor, which spins a gear against the flywheel or flex plate.
Where It’s Located: Starter locations vary by model. They are near where the transmission and engine join together. Some are visible from the engine bay.
57) Timing Belt
A timing belt is a toothed belt that synchronizes the rotation of the crankshaft with the camshafts. This allows the valves to open and close at precise points during the combustion cycle. They are often made out of rubber or polyurethane.
Where It’s Located: On the front of the engine, underneath the timing cover(s).
58) Timing Chain
A timing chain is essentially a metal timing belt. Timing chains typically do not require maintenance like a timing belt would, unless another engine component has failed.
Where It’s Located: On the front of the engine, underneath the timing cover(s).
Valves are metal plugs that regulate when air can enter or exit the engine. A closed valve prevents air from passing through the cylinder head.
Where It’s Located: Inside the cylinder head.
60) Valve Cover
A valve cover is a metal plate that covers the top of the cylinder head. Removing the valve cover will typically give you access to the camshafts and top of the valves.
Where It’s Located: On top of the engine. Some valve covers are colored for aesthetic purposes.
61) Valve Cover Gasket
A valve cover gasket is a rubber seal that helps contain oil in the cylinder head. Oil flows through the heads while the engine is running to lubricate the camshafts as they spin.
Where It’s Located: Between the valve cover and the cylinder head.
62) Valve Spring
Valve springs return the valves to a closed position after the cam lobe has pushed the valve open.
Where It’s Located: On top of the cylinder head.
63) Variable Valve Timing (VVT)
Variable valve timing is a system that allows the valves to open sooner or later, depending on performance needs. Advancing the timing at precise times gives the engine better power, efficiency, and fuel economy.
Where It’s Located: Variable valve timing is often implemented using special cam gear(s). Implementations vary by model.
64) Alternator (Generator)
An alternator charges the battery and powers the vehicle while the vehicle is running.
Where It’s Located: On the front or top of the engine. Alternators are typically visible when you first pop the hood.
A battery powers the vehicle when the engine is off. It provides enough amps to turn over the large starter motor when you turn the key.
Where It’s Located: Typically found in the engine bay. Some models may place the battery in the trunk or under a seat in the cabin instead.
66) Battery Post
A battery post looks like a metal stud sticking out of the top (typical) or side of a car battery. A normal car battery has two posts (positive and negative) which allow battery cable terminals (also positive and negative) a solid connection point.
Where It’s Located: On top of the battery.
67) Battery Terminal
A battery terminal connects the battery to the battery cables. These are made out of a conductive metal.
Where It’s Located: Connected to the battery posts.
68) Engine Control Unit/Module (ECU, ECM, or PCM)
The ECU is the main engine computer in the vehicle. This computer is in charge of fuel injection, ignition timing, engine performance monitoring, and sometimes auxiliary electronic systems such as stability control.
Where It’s Located: Typically found in the engine bay, but some models have an ECU inside the cabin instead.
A fuse is an electrical component that protects a circuit in case of a short or fault. Fuses have a thin metal wire inside that is designed to be the weak point in the circuit. The metal will melt if too much current is applied, protecting the rest of the circuit.
Where It’s Located: Inside a fuse box.
70) Fuse Box
A fuse box consolidates the fuses for many different circuits around the vehicle. Most vehicles have more than one fuse box.
Fuses are covered by a plastic panel that is easy to remove for quick fuse inspection.
Where It’s Located: Fuse boxes are typically found in the engine bay and under the dashboard.
71) Ignition Coil
Ignition coils convert low voltage from the battery into a voltage large enough to arc across the tip of a spark plug. Most modern vehicles use a coil-on-plug (COP) ignition, but older vehicles used a coil pack instead. Coil packs commonly shared ignition coils among multiple cylinders. This is called wasted spark ignition.
Where It’s Located: On top of the spark plugs.
A relay is an electrical switch that allows a high power component to be controlled via a low power signal. Relays have an internal mechanical component that you can hear click when it activates.
Where It’s Located: Inside a fuse box.
73) Spark Plug
A spark plug is a high voltage electrical component that ignites the air-fuel mixture during the combustion stroke. Spark plugs have a small gap that allows electricity to ark between them, igniting the fuel.
Where It’s Located: Inside the cylinder head.
74) Spark Plug Wire
A spark plug wire connects a spark plug to the coil pack. They are typically not used in a coil-on-plug ignition.
Where It’s Located: On top of a spark plug.
75) Catalytic Converter
A catalytic converter contains precious metals that convert toxic exhaust gases into less harmful compounds. Many vehicles have more than one catalytic converter.
Where It’s Located: Underneath the engine. Some catalytic converters are easily visible from underneath the car, but others are tucked up by the headers and harder to see.
76) Exhaust Gas Recirculation (EGR)
Exhaust gas recirculation is a system that routes some of the exhaust gases back into the intake in low load situations. This reduces the amount of space in the combustion chamber for the air-fuel mixture, helping the engine to run more efficiently when cruising.
Where It’s Located: Near the intake manifold or exhaust manifold.
77) Exhaust Manifold (Headers)
The exhaust manifold is the part of the exhaust system that connects to the cylinder head. When the exhaust valves open, their first stop is the exhaust manifold.
Where It’s Located: On one side of the cylinder head, sometimes underneath a heat shield. Be careful, they get very hot.
78) O2 Sensor (Oxygen Sensor)
An O2 sensor measures oxygen levels in the exhaust system. This tells the ECU how rich or lean to make the mixture. Most vehicles have more than one O2 sensor.
Where It’s Located: In the exhaust system. Many O2 sensors are easily visible underneath the car.
A muffler is a large chamber at the end of the exhaust designed to greatly reduce engine noise. Mufflers are made of several chambers that bounce sound around, canceling out the majority of unwanted noise. They also work as flame arresters, preventing open flames from exiting the exhaust.
Where It’s Located: The very back of the car.
80) Secondary Air Injection
Secondary air injection routes fresh air into the exhaust system on cold startup. It is an emissions control system.
Where It’s Located: Near the intake or exhaust system.
Boost is the amount of pressure in the intake above ambient atmospheric pressure. This is typically measured in pounds per square inch (psi) or bar. Standard atmospheric pressure is about 14.7 psi, or 1 bar.
Where It’s Located: Boost happens inside the engine, but most turbocharged cars have a boost gauge on the dashboard.
As air is compressed by a turbo or supercharger, it heats up from the extra pressure. Hot air is less dense and would therefore be less efficient. Intercoolers bring the charge air temperature back down, lowering the intake air temperatures in the combustion chamber.
Where It’s Located: On top or in front of the engine. They look like radiators, but for air instead of water.
A supercharger is a forced induction device that is driven by the crankshaft. As the supercharger spins, it compresses air via screws or compressor blades (like a turbo). There are several different types of superchargers, each with their own tradeoffs.
Where It’s Located: On top of the engine or next to the intake.
84) Turbocharger (Turbo)
A turbocharger is a forced induction device powered by exhaust gases. A turbo consists of a turbine and a compressor, each in a separate housing, connected by a shaft.
The turbine housing is part of the exhaust system, and the compressor housing is part of the intake system. As the exhaust gases spin the turbine, the compressor on the intake side forces air into the combustion chamber.
Where It’s Located: Turbos connect to both the intake and exhaust. Many are hidden deeper inside the engine bay but still visible from the outside if you have a flashlight.
Exhaust gases can usually spin a turbo faster than the engine can handle. To deal with this excess boost pressure, a wastegate routes excess exhaust around the turbocharger.
The ECU decides when to open and close the wastegate based on target boost pressures for a given ECU map. Aftermarket tuners can often adjust these values to give a vehicle increased performance.
Where It’s Located: Near the turbocharger.
86) Charcoal Canister
A charcoal canister is an emissions device designed to capture fuel vapors. These vapors may be routed to the intake or the fuel tank via the EVAP system.
Where It’s Located: Some are located in the engine bay, but other models place them by the fuel tank.
87) Direct Injection
Direct injection architectures place the fuel injector nozzles directly in the combustion chamber. Unlike port injection, allows for fuel injection to be controlled per cylinder, and typically leads to an increase in power and fuel economy.
Where It’s Located: In the cylinder head, just above the piston.
88) Dual Injection
Dual injection systems have two sets of injections, leveraging both port and direct injection. This type of injection strategy is uncommon.
Toyota uses dual injection on many of their modern vehicles (along with the Subaru BRZ, a Subaru that was developed in partnership with Toyota).
Where It’s Located: See Port Injection and Direct Injection.
89) Electronic Fuel Injection (EFI)
In an electronic fuel injection system, fuel delivery is controlled by an ECU instead of a carburetor. Nearly all vehicles made since 1990 use electronic fuel injection.
Where It’s Located:
The ECU is typically located in the engine near the battery, although other EFI components can be found on top of the engine.
90) EVAP System
The EVAP system is a sealed system of vacuum lines designed to contain fuel vapors. Fuel vapors pollute the environment and may even be a fire hazard in some instances. If you have a leak in your EVAP system, you can often smell the fuel.
Where It’s Located:
EVAP hoses connect to the fuel tank, charcoal canister, and the intake manifold. Also included are other emissions controls like the purge valve solenoid, which are typically found throughout the top of the engine bay.
91) Fuel Injectors
Fuel injectors spray fuel into the combustion chamber. They are designed to atomize fuel, which means the fuel is sprayed as a very fine mist. This helps the fuel burn very easily when the spark plug ignites it.
Where It’s Located: See Port Injection and Direct Injection.
92) Fuel Pressure Regulator
A fuel pressure regulator maintains adequate fuel pressure for the fuel injectors on a return-type fuel system. Excess pressure is routed back to the fuel tank. Returnless fuel systems use the ECU to regulate fuel pressure using a fuel pressure sensor instead.
Where It’s Located: Near the fuel rail.
93) Fuel Pump
A fuel pump draws fuel from the fuel tank and brings it to the engine. Low pressure fuel pumps typically sit in the fuel tank itself. High pressure fuel pumps are found in the engine bay on direct injected engines. High pressure fuel pumps allow the fuel pressure to overcome the intense pressures seen inside the combustion chamber.
Where It’s Located: Typically located in the top of the gas tank, some fuel pumps are accessible by removing the rear seats. Other models require you to drop the fuel tank to reach the fuel pump.
94) Fuel Rail
A fuel rail is the last stop in the fuel system before the fuel injectors. Injectors are typically mounted directly to the fuel rail.
Where It’s Located:
The fuel rail can typically be found on top of the engine, right next to the intake manifold.
95) Fuel Tank
A fuel tank houses the fuel for the vehicle. Most modern gasoline engines are designed to handle 10% ethanol in the fuel. Flex fuel vehicles are designed to handle higher ethanol content. Some can even run on 100% ethanol. E100 fuel is most common in Brazil.
Where It’s Located:
The fuel tank is located underneath the vehicle, typically towards the rear.
96) Port Fuel Injection
Port fuel injection systems inject fuel into “ports” in the intake manifold, rather than the combustion chamber. Since gasoline is a solvent, this setup has the added benefit of keeping the intake valves clean.
Where It’s Located:
Fuel injectors connect directly to the intake manifold in a port injection system.
Heating, Ventilation, and Air Conditioning (HVAC)
97) A/C Compressor
An A/C compressor is a cylindrical accessory that is driven off of the crankshaft like the alternator. When the A/C clutch is engaged, the compressor cools the air in the cabin.
Where It’s Located: On the front of the engine, driven by the accessory belt.
98) A/C Condenser
A condenser is like a radiator, but for the air conditioning system. It is designed to release heat collected by the air conditioning system as air passes through it.
Where It’s Located:
The condenser is located right next to the radiator. It is typically the smaller unit of the two, with a large hose on one side and a small hose on the other.
99) Cabin Air Filter (HVAC Filter)
The cabin air filter cleans the air inside the cabin. Some filters are HEPA filters that can even filter out smoke and foul smells.
Where It’s Located: Many cabin air filters can be found behind the glovebox.
100) Manifold Absolute Pressure Sensor (MAP Sensor)
A MAP sensor measures the pressure inside the intake manifold. They are typically used on speed density engine management systems.
Where It’s Located: On top of the intake manifold.
101) Mass Airflow Sensor (MAF Sensor)
A MAF sensor measures the amount of air that is flowing through the intake. MAF sensors use a very thin wire that is prone to dirt buildup if the engine air filter is not changed regularly.
Where It’s Located: Inside the intake tube, just behind the engine air filter.
102) Intake Air Temperature Sensor (IAT Sensor)
An IAT sensor measures the charge air temperature inside the air intake or intake manifold. Fuel delivery and ignition timing are adjusted based on IAT data. If the air is too hot, timing needs to be dialed back so the engine doesn’t knock.
Where It’s Located: Inside the intake or on top of the intake manifold.
103) Intake Manifold (Inlet Manifold)
An intake manifold attaches to the cylinder head and brings air (and sometimes fuel) to the combustion chamber.
Where It’s Located: On one side of the cylinder head.
104) PCV Valve
A Positive Crankcase Ventilation (PCV) valve routes excess crankcase pressure back to the intake.
Where It’s Located: Connected to the intake manifold via a vacuum hose.
105) Throttle Body
A throttle body connects to the gas pedal. When you step on the gas, the throttle opens to allow air to enter the engine. Older vehicles use a throttle cable to connect the gas pedal directly to the throttle body. Newer vehicles are drive by wire. A drive by wire vehicle uses a “requested torque” value to understand the driver’s intent, then translates this into a signal to open or close the throttle. Drive by wire systems allow the ECU to ignore driver input for automatic braking and collision avoidance, if equipped.
Where It’s Located: On top of the engine, just behind the engine air filter.
Other Powertrain Components
106) Axle (Half Shaft)
Axles connect driven wheels to a differential.
Where It’s Located: Axles connect the wheels to the drivetrain and can be seen from underneath the vehicle.
A differential takes torque as input from the transmission and splits it between two wheels or axles. Front and rear differentials split the torque from left to right. A center differential splits the torque from front to rear.
Where It’s Located: Rear differentials, if equipped, are easily visible from the back of the car. Front and center differentials may be integrated with the transmission, depending on the model. This integrated unit is commonly called a transaxle.
A driveshaft connects the transmission to a rear differential. Driveshafts are balanced to minimize noise and vibration.
Where It’s Located: Connects the transmission to the rear differential.
109) Hub Assembly
A hub assembly is the mounting surface for a wheel. Some hubs contain studs and a wheel speed sensor. Hubs have bearings so the face of the hub can spin freely with the wheel.
Where It’s Located: Connects the wheels to the car via lug nuts or lug bolts.
A transaxle integrates the transmission and differential(s) into a single unit. Transaxles are common on front wheel drive vehicles.
Where It’s Located: Mated to the engine. Most transaxles are to the side of the engine in the engine bay (transverse) or just behind the engine (longitudinal).
111) Transfer Case
A transfer case is found on 4×4 vehicles, allowing the driver to manually engage and disengage the front differential. Unlike a full-time AWD system, it’s generally not good for the powertrain to leave the transfer case in 4×4 mode all the time.
Where It’s Located: Next to the transmission on 4×4 and some AWD vehicles.
Safety and Restraint Systems
112) Airbag (Supplemental Restraint System or SRS)
An airbag is an inflatable “safety net” designed to gradually slow occupants during a crash.
Where It’s Located: Airbags are commonly found in steering wheels and above the glovebox. Side airbags are found in newer vehicles in the B pillars.
113) Airbag Module
An airbag module is a computer that controls the activation and monitors the health of the airbags in a vehicle.
Where It’s Located: Inside the cabin, under the dash or near the floor.
114) Forward Collision Warning System (FCW)
Forward collision warning systems use radar, lidar, or cameras to detect obstructions in a vehicle’s path and alert the driver. Some vehicles are also equipped with collision avoidance systems that will attempt to evade the obstacle.
Where It’s Located: FCW systems are part software and part hardware. You may notice a camera system behind your windshield. The software lives inside a control module.
115) Seat Belt
A seat belt is a restraint device intended to hold occupants in their seat. They are typically made out of a strong canvas.
Where It’s Located: Next to each seat.
116) Seat Belt Pretensioner
A seat belt pretensioner is designed to pull a seat belt tight during the first moments of a collision. A seat belt can only do its job when it is tight. This also pulls the occupants away from the airbags, giving them the maximum amount of space to slow down.
Where It’s Located: Near the bottom of each seatbelt.
117) Stability Control
Stability control systems measure the intended direction of travel of a vehicle. If the driver’s input does not match the actual direction of travel, the ABS system will engage and attempt to correct the vehicle’s trajectory.
Where It’s Located: Stability control systems are software, often stored in the ABS module or ECU.
118) Traction Control
Traction control systems measure wheel slip during acceleration. If you step on the gas and the tires spin, traction control will apply the brakes to individual wheels or reduce engine torque to maintain traction on each tire.
Where It’s Located: Traction control systems are software, often stored in the ABS module or ECU.
A coilover is a suspension component consisting of a shock and a spring. They are common aftermarket modifications, although many vehicles are equipped with them from the factory (particularly those with double wishbone suspension architectures).
Where It’s Located: Underneath the vehicle, connecting the wheels to the body.
120) Lower Control Arm
Lower control arms are a main structural component in most suspension systems. They connect the strut or shock to the body of the vehicle.
Where It’s Located: Underneath the vehicle, connecting the lower part of the hub to the frame or body of the vehicle.
121) Shock (Damper)
A shock or damper is a fluid-filled cylinder that limits the reciprocating motion of the springs in the suspension. This allows the spring to compress and rebound while remaining in contact with the road as much as possible.
Where It’s Located: Inside or next to the strut or spring.
A spring holds up each corner of the vehicle and provides cushioning when you drive over bumps. Softer springs give a more comfortable ride, but may require greater suspension travel.
Where It’s Located: Behind each wheel in the wheel well.
A strut is a structural member of the suspension containing a spring and shock. They differ from coilovers because they replace the upper control arm you’d typically find on a double wishbone suspension system.
Where It’s Located: Behind each wheel in the wheel well.
124) Top Hat
A top hat is the top of the strut or coilover. The top hat compresses the spring slightly and holds the coilover or strut assembly together.
Where It’s Located: On top of a strut or coilover.
125) Upper Control Arm
An upper control arm is the top arm of a double wishbone suspension system.
Where It’s Located: Connects the top of the hub to the body in a double wishbone suspension system.
A clutch uses friction to link the engine to the transmission. When the clutch is engaged, the engine and input shaft of the transmission spin at the same speed.
Where It’s Located: Between the engine and the transmission on a manual transmission vehicle.
127) Clutch Fork
A clutch fork is a level that separates the clutch from the flywheel when the clutch pedal is pressed.
Where It’s Located: Between the slave cylinder and the throwout bearing, attached to a manual transmission.
128) Clutch Master Cylinder
The clutch master cylinder is connected to the clutch pedal and uses a piston to compress the clutch fluid, allowing the driver to disengage the clutch.
Where It’s Located: Inside the engine bay. Some clutch master cylinders share a reservoir with the brake master cylinder.
129) Clutch Slave Cylinder
A clutch slave cylinder sits near the transmission and pushes on the clutch fork, allowing the driver to disengage the clutch.
Where It’s Located: Near the transmission, attached to the clutch fork.
130) Flex Plate
A flex plate is a large gear that is bolted to the back of the engine, allowing the starter to turn the engine. It is only found on automatic transmissions.
Where It’s Located: Between the engine and transmission of an automatic transmission vehicle.
A flywheel is a large metal disc that helps preserve angular momentum. This smooths out a vehicle’s idle and makes a manual transmission easier to drive.
Where It’s Located: Between the engine and transmission of a manual transmission vehicle.
132) Input Shaft
The input shaft in an automatic transmission is connected to the engine on one end and torque converter on the other. It’s responsible for bringing in power to the transmission.
Where It’s Located: On the front of the transmission.
133) Output Shaft
The output shaft in an automatic transmission is responsible for transmitting power from the transmission out to the wheels.
Where It’s Located: On the rear of the transmission.
134) Pilot Bearing
A pilot bearing sits on the end of the crankshaft, allowing a speed difference between the crankshaft and the input shaft of the transmission.
Where It’s Located: At the back of the crankshaft, between the engine and the transmission.
135) Pressure Plate
A pressure plate is part of the clutch assembly that contains spring-like fingers. These fingers separate the clutch from the flywheel when the clutch pedal is pressed.
Where It’s Located: Between the engine and a manual transmission.
136) Shifter (Gear Stick)
A shifter allows the driver to select forward gears, park, or place the vehicle in reverse.
Where It’s Located: Inside the cabin between the front seats.
137) Synchronizer (Synchro)
Synchros allows a driver of a manual transmission to change gears smoothly, even when the wheel speed and engine speed do not match exactly. They are typically made of a soft metal like brass.
Where It’s Located: Inside the transmission.
138) Throwout Bearing (Clutch Release Bearing)
A throwout bearing transfers the pressure applied from the clutch fork to the fingers of the pressure plate.
Where It’s Located: On the front of the transmission.
139) Torque Converter
A torque converter is a drum-shaped component filled with transmission fluid. It is housed between the back of the engine and the transmission on many automatic and CVT transmissions.
Torque converters transfer engine torque to the transmission gradually, allowing slip like a clutch would. Like a flywheel, it helps preserve angular momentum.
Where It’s Located: Between the engine and the transmission on automatic transmissions.
140) Transmission Control Module (TCM or TCU)
A transmission control module is the computer that monitors and controls the operation of an automatic transmission. The TCM is responsible for when and how to shift. More sophisticated TCMs will automatically downshift for you when you brake on a hill, for instance.
Where It’s Located: Often found on top of the transmission.
141) Valve Body
A valve body is a maze-like structure that routes transmission fluid through an automatic transmission. Valve bodies are fluid-filed circuits that use solenoids to direct fluid where it needs to go, based on input from the TCM.
Where It’s Located: Underneath an automatic transmission.
142) Vehicle Speed Sensor (VSS)
Speed sensors read measure the speed of the transmission. This information is displayed in the speedometer and odometer on the instrument cluster.
Where It’s Located: On top of the transmission.
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