The exhaust gas recirculation (EGR) system is used to lower oxides of nitrogen (NOx) emission levels caused by high combustion temperature. The system does this by decreasing the combustion temperatures.

The main element of the system is the linear EGR valve. The EGR valve feeds small amounts of exhaust gas back into the combustion chamber. With the fuel/air mixture thus diluted, the combustion temperatures are reduced.

The linear EGR valve is designed to accurately supply EGR to an engine independent of the intake manifold vacuum. The valve controls the EGR flow from the exhaust to the intake manifold through an orifice with a PCM-controlled pintle. During operation, the PCM controls the pintle position by monitoring the pintle position feedback signal. The feedback signal can be monitored with a scan tool. The actual EGR position should always be near the commanded EGR position. If a problem with the EGR system will not allow the PCM to control the pintle position properly, DTC P0404 should set. The PCM also tests for EGR flow. If an incorrect flow is detected, DTC P0401 should set.

The linear EGR valve is usually activated under the following conditions:

The PCM monitors the actual EGR position and adjusts the pintle position accordingly. The PCM uses information from the following sensors to control the pintle position: