What is the function of the EGR valve?

• A. It regulates fuel pressure to the injectors.
• B. It controls throttle position.
• C. It recirculates exhaust gas back into the intake to reduce NOx emissions and control combustion temperatures.
• D. It modulates radiator cooling fan speed.

Answer: (D)

The function of the EGR valve is to recirculate a portion of the exhaust gas back into the intake manifold. This dilutes the incoming air–fuel mixture with inert exhaust gas, which lowers the peak combustion temperature. Lower temperatures reduce the formation of nitrogen oxides (NOx), helping the engine meet emissions requirements. The EGR system is typically active under certain engine loads and speeds to balance emissions reduction with engine performance. Other functions listed—regulating fuel pressure to the injectors, controlling throttle position, and modulating radiator cooling fan speed—are handled by different systems and components.