Air Fuel Ratio (A/F) Sensor
The job of the air fuel ratio sensor is to measure the oxygen content in the exhaust and provide the feedback to the engine computer (PCM). Based on air fuel ratio sensor signal, the computer adjusts the air to fuel ratio
Alternator
An alternator is attached to the engine and run by a drive belt. When the engine is running, an alternator generates electric power to charge the battery. An alternator doesn't need any maintenance, but it can fail with mileage
Blower Motor Resistor
A blower motor resistor controls the speed of the blower motor in the manual HVAC system. One of the symptoms of a failed blower motor resistor is when the heating system fan only works at the highest speed setting
Check Engine Light
The Check Engine light is the source of frustration of many motorists. Dealing with this problem takes time and money, but there are several things you can check yourself. There are many options to have your car repaired.
Brake Light Switch
The brake light switch serves two major functions. First, it turns on the brake lights when a driver presses the brake pedal. Second, it sends the signal to the vehicle computer that brakes are applied.
Crankshaft Position Sensor
The crankshaft position sensor measures the rotation speed (RPMs) and the precise position of the engine crankshaft. Without a crankshaft position sensor the engine wouldn't start.
CV Joints
Constant Velocity (CV) joints transfer the torque to the drive wheels, while accommodating the up-and-down movement of the suspension and the steering action. CV joints are packed with special grease and sealed by a rubber boot.
DOHC Engine
DOHC means Double OverHead Cam, or sometimes it could be called "Twin Cam" or "Double Cam." Most modern cars have DOHC engines. A typical DOHC engine has two camshafts and 4 valves per cylinder.
Control Arm
One of the main components of the front suspension, the control arm connects the front wheel to the vehicle's chassis. In many cars, a ball joint is built into the control arm as one piece
Door Lock Actuator
The door lock actuator is an electrically-powered device that operates the door latch mechanism. In many cars, the door lock actuator is built with the latch mechanism into one assembly.
Drive Belt
A drive or serpentine belt runs accessories attached to the engine such as an alternator, power steering pump, water pump and air conditioner compressor. Over time, a drive belt wears and must be replaced.
Engine Mount
An engine mount hold the engine to the vehicle's body or frame. Some engine mounts are filled with liquid and work similar to a shock absorber. This design helps reduce the engine vibration felt inside the cabin.
Auto Glossary
Ignition Coil
An ignition coil is a part of the vehicle's ignition system. It converts 12V battery power into high voltage in order to create a spark at a spark plug. The spark ignites the air/fuel mixture in the engine cylinders.
Intake Manifold
An intake manifold distributes the intake air flow evenly between cylinders. In many cars, an intake manifold also hosts the throttle valve (throttle body). An intake manifold consists of the plenum and the runners.
OHC or SOHC Engine
OHC means OverHead Cam in general, while SOHC means Single OverHead Cam or Single Cam. In a SOHC engine the camshaft is installed in the cylinder head and valves are operated either by the rocker arms or directly through the lifters.
OHV Engine
OHV in general means OverHead Valve. Often the term "OHV" is used to describe the "Pushrod" engine design where the camshaft is installed inside the engine block and valves are operated through lifters, pushrods and rocker arms.
Oxygen Sensor
An oxygen sensor (O2 sensor) measures the amount of oxygen in the exhaust gases, sending the signal to the engine computer. A front oxygen sensor is installed in the exhaust before the catalytic converter.
Purge Valve
The Evaporative Control (EVAP) system traps fuel vapors from the fuel tank and stores them in the charcoal canister. The purge valve controls the flow of the fuel vapors from the charcoal canister.-
Serpentine Belt
A serpentine belt runs the accessories such as an alternator, power steering pump, water pump and air conditioner compressor. Over time, a serpentine belt wears and must be replaced. 
Starter Motor
A starter is an electric motor that turns over or "cranks" the engine to start it. To turn over the engine the starter motor requires a very high electric current, which means the battery has to have sufficient power.
Steering U-joint
A steering u-joint has four needle bearings packed with grease and sealed. A failed steering u-joint could cause a knocking noise in the steering. The steering also could become stiffer at certain angles.
Thermostat
The thermostat is an important part of the engine cooling system. It helps the warm the engine up faster and maintain the proper operating temperature. One of the symptoms of a bad thermostat is lack of heat when driving on a highway.
Timing Belt
A timing belt connect the engine crankshaft with the camshaft(s) to time the opening and closing of the valves with the movement of the pistons. In some cars, an engine may get severely damaged if the timing belt brakes.
EVAP Vent Valve
A Vent valve is a vital part of the Evaporative Control (EVAP) system. The EVAP system is responsible for traping fuel vapors from the fuel tank and burning them in the engine. Problems with a vent valve will cause the3 Check Engine light to come on.