DTC P0401: EGR Flow Insufficient: Description

Exhaust Gas Recirculation (EGR) valve consists of a pintle valve which moves by use of an internal solenoid and internal position sensor (potentiometer) used to determine pintle valve position. PCM controls solenoid by supplying it ignition voltage whenever exhaust gas needs to be recirculated into intake manifold. PCM monitors EGR solenoid and position sensor circuit for correct voltage levels at certain times. PCM also monitors flow of exhaust gas through EGR valve by using MAP sensor. During deceleration, EGR valve is normally closed. However, PCM will run a flow test by opening EGR valve and monitoring change in MAP signal voltage. DTC sets when change in MAP signal voltage is less than a certain threshold when EGR valve is being commanded on during deceleration.