EGR — aust Gas Recirculation

EGR routes a portion of exhaust gases back into the intake manifold to reduce combustion temperature and NOx emissions. The ECU controls EGR position via a stepper motor or electric valve and monitors flow via differential pressure sensors.

EGR is the #1 failure point on modern diesels. Carbon from exhaust gases mixes with oil vapour from the PCV system and forms a hard coating that sticks the EGR valve open or closed, throws DTCs (P0401-P0408), and clogs the intake manifold. Tuners apply EGR OFF after fitting a blanking plate to prevent recurrence.