DTC P0401: EGR Flow Insufficient: Description

The Engine Control Module (ECM) tests the flow of the Exhaust Gas Recirculation (EGR) system during steady state driving conditions. The ECM does this by momentarily commanding the EGR valve to open while monitoring the signal of the Manifold Absolute Pressure (MAP) sensor. The ECM performs one flow test per ignition cycle. When the EGR valve is opened, the ECM will expect to see a predicted increase in MAP. If the ECM detects a less than predicted increase in MAP, DTC P0401 sets.