DTC P1404: EGR Closed 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 valve responds properly to commands from PCM. When ignition is turned on, PCM learns EGR learned minimum position. PCM compares EGR learned minimum position to EGR position sensor when EGR valve is commanded closed. DTC sets when EGR position sensor indicates EGR valve is still open when PCM is commanding EGR valve closed.