Exhaust Gas Recirculation: Description and Operation

Linear EGR Valve:

The Exhaust Gas Recirculation (EGR) system is used to lower Oxides of Nitrogen (NOx) emission levels caused by high combustion temperature. It does this by decreasing combustion temperature.

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 diluted by the exhaust gases, combustion temperatures are reduced.

The valve controls EGR flow from the exhaust to the intake manifold through an orifice with a PCM controlled pintle. During operation, the PCM controls pintle position by monitoring the pintle position feedback signal. If a problem with the EGR system will not allow the PCM to control pintle position properly, DTC P1406 should set. The PCM also tests for EGR flow; if incorrect flow is detected, DTC P0401 should set.