The document describes the internal exhaust gas recirculation (IEGR) system used on the engine. The IEGR system uses a hydraulic mechanism located in IEGR units on the rocker arm holders. When activated by the ECU, a solenoid valve allows oil flow to the IEGR unit which increases pressure and causes a servo piston to open the exhaust valve for a short time during induction. This allows some exhaust gases to reenter the cylinder, reducing NOx formation. The system precisely controls exhaust gas recirculation through hydraulic components like the main piston, control valve, and servo piston.