EGR System Operation

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

The EGR valve is controlled by the engine control module (ECM) through the EGR motor high control and low control circuits. The ECM supplies voltage that is near ignition voltage to the high and low control circuits at all times. This voltage is used by the ECM as a reference voltage during non EGR operation in order to detect circuit failures. When the EGR valve is commanded open, the ECM pulse width modulates (PWM) the low control circuit to ground and the high control circuit sees an increase in current. A lower pulse width will increase the open position of the valve. To close the EGR valve, the ECM will PWM the high control circuit to ground.

When the ignition is turned OFF, the EGR valve executes a series of clean and learn operations. The valve goes through a number of full sweeps, (cleaning operation), followed by a number of learn events that pushes the poppet off the seat and then the spring forces it back into the seat to determine the correct sensor position voltage. Certain environmental conditions, such as low temperature, may inhibit the clean and learn operations, so they may not occur during every ignition cycle.

The EGR valve contains an integral valve position sensor which reflects the true position of the valve. The ECM uses the position sensor on the EGR valve to determine the position of the EGR valve. The ECM sends a reference voltage through the 5 V reference circuit to the position sensor. The ECM provides a voltage return path for the sensor through the low reference circuit. A variable voltage signal, based on the valve position, is sent from the sensor to the ECM through the position sensor signal circuit.

The mass air flow (MAF) sensor signal is used by the ECM to detect the proper amount of EGR flow. The ECM continually does a consistency check on the indicated EGR flow by comparing the desired MAF to the actual MAF. If the actual MAF is less than or greater than a calibrated threshold level, the amount of EGR flow is determined to be out of range and a DTC will set.

EGR Valve Control Enabling Conditions

EGR valve control will only be enabled during idle and cruising conditions while the following conditions are met:

Intake air temperature (IAT) is greater than 5.3°C (41.5°F). EGR valve control will remain enabled until the IAT is less than 0°C (32°F) and will not enable again until the IAT is greater than 5.3°C (41.5°F).
Engine coolant temperature (ECT) is between 60-97°C (140-207°F). EGR valve control will remain enabled until the ECT is less than 57°C (134.6°F) or greater than 100°C (212°F) and will not enable again until the ECT is between 60-97°C (140-207°F).
Barometric pressure (BARO) is greater than 74 kPa (10.73 PSI). EGR valve control will remain enabled until BARO is less than 72 kPa (10.44 PSI) and will not enable again until greater than 74 kPa (10.73 PSI).