When does EGR valve opens?

The Exhaust Gas Recirculation (EGR) valve opens during specific engine operating conditions, primarily when the engine is at moderate to high loads and temperatures. This typically occurs when the engine is warmed up and running at cruising speeds, allowing a portion of the exhaust gases to be recirculated back into the intake manifold. This process helps reduce nitrogen oxide (NOx) emissions by lowering the combustion temperature. The exact timing can vary based on the vehicle's design and the engine management system.