Final answer:
The EPA defines a major repair as the replacement of catalytic converters, oxygen sensors, electronic control units, and fuel injectors. These components are integral to a vehicle's emissions control system, and their proper functionality ensures compliance with environmental standards.
Step-by-step explanation:
The question pertains to what the Environmental Protection Agency (EPA) considers to be a major repair in the context of vehicle maintenance and emissions control. According to the EPA, a major repair usually involves the replacement of any of the four key components: catalytic converters, oxygen sensors, electronic control units (ECUs), and fuel injectors. These components are crucial for the proper functioning of a vehicle's emissions control system, and their replacement can significantly affect the vehicle's environmental impact.Step-by-step explanation: The catalytic converter plays a vital role in reducing harmful emissions by converting toxic gases such as carbon monoxide, nitrogen oxides, and hydrocarbons into less harmful substances like carbon dioxide, nitrogen, and water vapor. The oxygen sensor monitors the level of oxygen in the exhaust to help the ECU regulate the fuel-air mixture for optimal combustion. An ECU controls the engine's operation and is essential for adjusting performance and efficiency. Lastly, the fuel injectors are responsible for delivering the correct amount of fuel to the engine.Conclusion: These replacements are regarded as major due to the complexity of the procedures and the significant role each part plays in reducing vehicle emissions. Regular maintenance and timely replacement of these components are critical for maintaining a vehicle’s efficiency and compliance with environmental standards.