DTC P0401: EGR System Failure: Description

EGR system is monitored with ignition on and battery voltage more than 10.4 volts. DTC will set in Powertrain Control Module (PCM) memory when PCM detects too little or too much of a change in oxygen sensor output signal when EGR is turned off then on. Possible causes are: EGR valve open at idle, EGR solenoid control circuit open or shorted, defective EGR valve, defective EGR solenoid, Auto Shutdown (ASD) relay output circuit open or defective PCM.