Car Parts Explained
What each part actually does, how it works, the symptoms when it fails, and the trouble codes it sets — in plain language. New components are added regularly.
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Alternator
The alternator is the vehicle's power plant: spun by the engine's belt, it generates the electricity that runs everything and recharges the battery.
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Catalytic Converter
The catalytic converter is a chemical reactor in your exhaust that converts the engine's three worst pollutants into carbon dioxide, water, and nitrogen, using precious-metal coatings at high temperature.
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EGR Valve (Exhaust Gas Recirculation)
The EGR valve routes a measured dose of exhaust gas back into the intake.
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Fuel Injector
A fuel injector is an electrically-controlled valve that sprays a precisely measured mist of fuel for combustion — opening and closing in milliseconds, thousands of times per minute.
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Ignition Coil
An ignition coil is a compact transformer that turns the battery's 12 volts into the 25,000–45,000 volts a spark plug needs to ignite the mixture.
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Mass Air Flow (MAF) Sensor
The MAF sensor measures exactly how much air enters the engine — the single number all fuel delivery is calculated from.
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Oxygen Sensor (O2 Sensor)
An oxygen sensor measures how much oxygen remains in the exhaust and reports it to the engine computer many times per second, letting it fine-tune the fuel mixture in real time.
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Thermostat (Engine Cooling)
The thermostat is a temperature-operated valve that blocks coolant flow to the radiator until the engine warms up, then continuously regulates flow to hold operating temperature.