DTC P1404: EGR System (Valve No. 2): Description
WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
The Exhaust Gas Recirculation (EGR) valve position sensor is monitored by the Powertrain Control Module (PCM). The 5-volt reference circuit, low reference circuit and EGR valve position signal circuit are used by the PCM to determine the EGR valve position. When ignition is turned on, PCM records the EGR Learned Minimum Position. The PCM compares the EGR Learned Minimum Position parameter to the EGR Position Sensor parameter. If PCM detects that the EGR valve is still open when the PCM is commanding the EGR valve closed, DTC P1404 sets.