DTC P0404: EGR Open Position Performance: Description
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 Pontiac Grand Prix, 2002 Pontiac Bonneville, 2002 Chevrolet Monte Carlo, 2002 Chevrolet Impala, and 2002 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
Powertrain Control Module (PCM) monitors Exhaust Gas Recirculation (EGR) valve pintle position input to ensure that valve responds properly to commands from PCM. PCM compares EGR position sensor with desired EGR position when valve is commanded open. DTC sets when difference between EGR position sensor and desired EGR position is more than 15 percent.