EGR System - Diesel: Operation
EGR valve is located on intake manifold. It introduces exhaust gases to incoming fresh air at engine crossover. EPR valve is located between exhaust manifold and exhaust pipe, and is used to increase exhaust backpressure during idle which increases exhaust flow through the EGR system. TPS is located on throttle shaft of injection pump. As throttle is opened, one switch contact opens a circuit and another switch closes a circuit at calibrated throttle angles.