Diagnostic Trouble Codes – P0401, P0402, P0403, P0404, P0405, P0406
Description
P0401 – EGR Flow Insufficient Detected
P0402 – EGR Flow Excessive Detected
P0403 – EGR Control Circuits
P0404 – EGR Control Circuit Range/Performance
P0405 – EGR Sensor A Circuit Low
P0406 – EGR Sensor A Circuit High
The Exhaust Gas Recirculation (EGR) system’s purpose is to redirect exhaust gas back into the cylinders. Since exhaust gas is inert (it won’t burn), it displaces oxygen and fuel, thereby lowering cylinder temperatures, which in turn lowers oxides of nitrogen emissions. For that reason, it needs to be carefully metered into the cylinders (via the EGR valve) so as not to adversely affect the engine’s performance. (Too much EGR and the engine won’t idle.)
The contents of HotShotsSecret.com, such as text, graphics, images, and other material contained on the Diagnose Your Diesel section are for informational purposes only. Always seek the advice of your mechanic or other qualified professional with any questions you may have regarding your vehicle’s condition.