DTC P0404: EGR Valve Open Pintle Position: 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 Powertrain Control Module (PCM) monitors the Exhaust Gas Recirculation (EGR) valve pintle position input to ensure that the valve responds properly to commands from the PCM. The PCM compares the EGR position sensor with desired EGR position when the valve is commanded open. If the difference between the EGR position sensor and Desired EGR Position is more than 15 percent, this DTC will set.