DTC P0406 (2017): General Description
The exhaust gas recirculation (EGR) system reduces oxides of nitrogen (NOx). NOx is generated by high combustion temperatures. The EGR system lowers peak combustion temperature by recirculating inert exhaust gas into the air/fuel mixture, thus reducing NOx emissions. To determine the optimal amount of recirculating exhaust gas, depending on driving conditions, a command value (the amount of valve lift) is stored in the powertrain control module (PCM). The EGR valve position sensor indicates the amount of valve lift, and the PCM controls the EGR valve so that the amount of actual valve lift equals the command value by comparing the command value and the actual amount of valve lift. If the EGR valve position sensor output voltage is not within a specified value, the PCM detects a malfunction and stores a DTC.