DTC P0401: Exhaust Gas RECIRCULATION Flow Insufficient: Description

Powertrain Control Module (PCM) tests Exhaust Gas Recirculation (EGR) system during deceleration by momentarily commanding EGR valve open while monitoring Manifold Absolute Pressure (MAP) sensor signal. When EGR valve is opened, the PCM should see a proportional increase in MAP. If expected increase in MAP is not seen, PCM notes amount of error that was detected and adjusts an internal failure counter toward a failure threshold level. When failure counter exceeds failure threshold level, PCM will set Diagnostic Trouble Code (DTC) P0401.