99 toyota camry

EGR is "exhaust gas recirculation" - part of the emission control systems When combustion temperatures get too high, the nitrogen becomes unstable and attaches to oxygen creating NOX, so the EGR valve recirculates some exhaust gas back into the cylinders. Oddly the hot exhaust gases actually reduce temperature because there is less fuel to burn. There is also a vacuum modulator right next to the EGR valve that controls its operation based on engine vacuum. The most common problem with EGR valves, is that carbon in the exhaust accumulates on the pintel (?) (the part of the valve that moves) and causes it to stick. So the most common cure for EGR valve malfunction is simply to clean the valve.

Try cleaning first before replacing any component of the very simple system.