Low Pressure EGR Operation

WARNING: This page is about a different variant/trim than selected.

The low pressure EGR system is the desired system for EGR flow when the engine is warm because the low pressure EGR exhaust gas temperature and pressure is lower post Diesel Particulate Filter (DPF) and the exhaust gases are cleaner since soot is removed by the DPF. This allows the low pressure EGR to be introduced to the air intake system in front of the turbocharger. The Powertrain Control Module (PCM) will start to open the low pressure EGR valve when the following conditions are met:

The engine coolant temperature increases above 55°C (131°F)
The inlet air temperature pre turbo is above 16°C (60.8°F)
The boost temperature post turbo is below 190°C (374°F)

The exhaust gases in the low pressure EGR pass through a cooler to the EGR valve. The low pressure EGR cooler does not have a bypass valve since the low pressure EGR is not operated when the engine is cold. The EGR temperature sensor is located in the path between the EGR cooler and EGR valve. The Powertrain Control Module (PCM) monitors the temperature sensor signal to determine flow of the system based on commanded EGR valve position.

The Powertrain Control Module (PCM) calculates the flow rate of the low pressure EGR system and compares it to the commanded EGR flow rate. In order to calculate the low pressure EGR flow rate, the PCM monitors the input signals from the DPF differential pressure sensor, EGR temperature sensor and inlet air temperature sensor. If the PCM determines that the low pressure EGR cannot produce enough flow, it will commanded the exhaust valve actuator partially closed to increase EGR flow. If the PCM determines that the DPF is cracked, based on feedback from the DPF differential pressure sensor, the low pressure system will be disabled.