The Exhaust Gas Recirculation (EGR) system is designed to reintroduce exhaust gas into the combustion chambers, thereby lowering combustion temperatures and reducing the formation of Oxides of Nitrogen (NOx).
The amount of exhaust gas that is reintroduced into the combustion cycle is determined by several factors, such as: engine speed, engine vacuum, exhaust system backpressure, coolant temperature, throttle position. All EGR valves are vacuum operated. The EGR vacuum diagram for your particular vehicle is displayed on the Vehicle Emission Control Information (VECI) label.
The EGR system is a Pressure Feedback EGR (PFE) or Differential PFE (DPFE) system, controlled by the Powertrain Control Module (PCM) and composed of the following components: PFE or DPFE sensor (also referred to as the backpressure transducer), EGR Vacuum Regulator (EVR) solenoid, EGR valve, and assorted hoses and tubing.
| Fig. 1: Typical EGR system schematic
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