I have been a certified automotive technician for 15 years now and a published author with Pearson Publishing in Automotive Technologies, and I currently teach professional technicians to be better professional technicians. When it comes to vehicles, I think I understand how a doctor feels when it comes to getting questions about their profession. I get asked all the time what a specific component is and what it does. So, here are three common automotive components that have acronyms, what the acronyms mean, and what the individual components do.
What is a PCV valve? Positive crankcase ventilation valve.
This valve is important because it helps vent the pressure that can build up in the engine while it is running. It opens when any pressure that is higher that 2 psi (pounds per square inch) exists and vents it to the engine intake, where it can be burned in the combustion chamber. If the engine does not have this valve working properly, too much pressure can build up in the oil pan and engine block and cause leaks. In turn, this causes excessive pressure on gaskets (seals that prevent leaks from one part to another), which can lead to oil dripping in your driveway. This was the very first piece of automotive emissions equipment required on a vehicle. Before the PCV valve existed, oil and crankcase pressure was just vented to the ground.
What is an EGR valve? Exhaust gas recycle valve.
The purpose of this valve is to recycle gases from the exhaust that have not been completely burned from the process of combustion. The EGR valve helps to lower vehicle emissions by recycling the air in the exhaust back into the engine to be reburned.
What is an O2 sensor? Oxygen sensor.
The sole purpose of this sensor is to determine the amount of oxygen that comes out of the engine from the combustion process into the exhaust. This information is important to the Engine Control Module when determining fuel to air ratio mixture.
These components are all emissions components. The only component of the three discussed that needs to be checked and replaced regularly is the PCV valve. A well-trained technician will be able to tell if it needs replacing. The O2 sensor and the EGR valve are tested regularly by the vehicle itself, and a check-engine light will go on if a problem is found with either one. Remember that if the check-engine light is present, it is to inform you of a problem. The quicker you get it fixed, the more money and fuel you will save, and the better our air quality will be.