DTC P0403: EGR Solenoid Control Circuit: 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. Linear EGR valve is controlled by using an ignition positive driver and ground circuit within PCM. Driver has ability to detect an electrical malfunction in ignition positive or ground circuit. If an electrical malfunction occurs, driver signals PCM to set this DTC.