Exhaust Gas Recirculation (EGR) System
Overview
The EGR system controls the NOX emissions. Small amounts of exhaust gases are recirculated back into the combustion chamber to mix with the air to fuel charge. The combustion chamber temperature is reduced, lowering NOX emissions.
Exhaust Gas Recirculation (EGR) System
The EGR system consists of an electric motor EGR valve integrated assembly, a MAP sensor, differential pressure feedback EGR sensor, PCM, EGR cooler, exhaust pressure (EP) sensor, and EGR temperature bank 1, sensor 2 (EGRT12). Operation of the system is as follows:
The EGR system receives signals from the ECT or CHT sensor, TP sensor, CKP sensor, and the MAP sensor to provide information on engine operating conditions to the PCM. The engine must be warm, stable, and running at a moderate load and RPM before the EGR system is activated. The PCM deactivates the EGR during idle, extended wide open throttle (WOT), or whenever a concern is detected in an EGR component or EGR required input. The PCM calculates the desired amount of EGR for a given set of engine operating conditions.
The exhaust pressure sensor determines EGR cooler effectiveness and converts EGR flow to EGR valve position.
The EGRT12 sensor measures the exhaust gas temperature downstream of the EGR cooler and is monitored by comparing the EGRT sensor calibrated value to the actual EGRT sensor value. The EGRT12 sensor is used for EGR flow calculation and EGR cooler diagnostics.
The intake manifold pressure is higher when the EGR is flowing than when it is not flowing. When the exhaust gas is delivered into the intake manifold, the MAP sensor reading increases.
The exhaust manifold provides a source of exhaust gas to the EGR cooler, EGR orifice tube, and EGR valve.
The EGR cooler is monitored by comparing the EGRT12 and exhaust pressure sensors calibrated value to the actual EGRT12 and exhaust pressure sensor values. Under cooling and over cooling conditions are monitored.