Oxygen Sensor/EGO Sensor
Measures the percentage of oxygen in the exhaust, and tells the computer whether the fuel/air mixture is too lean or too rich.

Crankshaft or Camshaft Position Sensor/CPS
Monitors the rotation of the engine and tells the computer exactly when to trigger the fuel injectors or the ignition spark.

Ignition Wires
Carries the spark voltage to the spark plugs. Faulty wires can drain off the voltage to the spark plug and cause misfiring.

Mass Air Flow Sensor/MAF Sensor
Measures the amount of air drawn through the engine's air intake, so the computer can compensate for altitude and temperature.

MAP Sensor/BAP Sensor
Reads changes in barometric (air) pressure. The ECM uses this information to adjust timing advance and air/fuel ratio.

Distributor Cap/Rotor
Routes the ignition coil's output voltage to the correct spark plug. A faulty cap or rotor will cause the engine to misfire or refuse to start.

Detonation Sensor/Knock Sensor
Listens for engine "ping" so the ECM can retard the spark timing, and thereby reduce emissions and overheating, if the engine is knocking.

Ignition Coil
Convert's the car battery's 12 bolts to the thousands of volts needed to fire the spark plugs.

Air Pump Check Valve
One-way that valve  that prevents hot exhaust gases from recirculating back through the air pump, protecting the air bypass system.

Fuel Pump
Feeds fuel from the gas tand to the carburetor or fuel injection system. Most fuel-injected cars have electric fuel pumps

Mixture Control Solenoid
Used on computer-controlled carburetors. Controls the blend of air and fuel to produce the needed amount of power and minimize emissions.

Idle Speed Control Actuator
Adjusts idle speed as dictated by the ECM, to prevent idle fluctuations and keep emissions low.

EGR Valve Position Sensor
Detectors the opening of the EGR valve, so the ECM can make adjustments to optimize performance.

Control Module/Igniter
Regulates and times the spark signal to the ignition coil, for correct ignition without misfiring.

Ported Vacuum Switch
Senses engine temperature, and opens or closes vacuum lines to various emissions-related components.

EGR Valve
Recirculates a measured amount of exhaust gas into the engine's air intake, to lower combustion temperatures and reduce emissions, especially NOx.

Throttle Position Sensor/TPS
Monitors the position of the accelerator pedal and the throttle linkage, so the ECM can make accurate air/fuel mixture adjustments.

Coolant Temperature Sensor/CTS
Measures the temperature in the cooling system, so the ECM can make adjustments based on the engine's  operating temperature. Can also control the dashboard warning light.

Air Cleaner Temperature Sensor
Prevents cold outside air from entering the air intake until the engine warms up. This limits emissions and improves cold-engine performance.

PCV Valve/Positive Crankcase Ventilation Valve
Recirculates partially-burned gases from the crankcase to the combustion chamber, to improve economy and reduce emissions while preventing buildup of sludge and corrosion.

Voltage Regulator
Controls the voltage supplied to the car's electrical system, preventing overcharge, undercharge and damage to electrical computers

Fuel Injector
Injects fuel into the intake manifold. The ECM tells the injector exactly when to inject, and how much to inject, to produce the needed amount of power.

Breather Element
Filters out contaminants from the crankcase gases that are being drawn into the intake system throughout the PCV Valve.