17-2
1. Exhaust Gas Recirculation System
1.1 Overview
• EGR mixes inert gases contained in burned exhaust gases with the air on the inlet side (inlet manifold), thereby
reducing the combustion temperature and thus reducing the amount of harmful NOx (nitrogen oxides) contained
in the exhaust gases.
The EGR cooler provides cooling to increase the density of the inert gases, thereby achieving a greater EGR ef-
fect.
• The EGR system uses various sensors to detect engine operating conditions (engine speed, coolant temperature,
accelerator opening) and, based on the information obtained, lets the engine ECU control operation of the EGR
solenoid valve. (See Gr13E for the electronic control system and ECU connection diagram.)
• If black smoke occurs or the engine speed becomes erratic under heavy or low load condition of the engine, the
EGR valve control function is suspended.
STRUCTURE AND OPERATION
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