Circuit/System Verification
WARNING: This page is about a different car, the 2006 Chevrolet Monte Carlo and 2006 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
With the scan tool installed, observe the Engine Oil Pressure Sensor parameter in the IPC ECM/PCM Data List. With the engine idling, the EOP sensor parameter should indicate a range of 0.7 volts - 2.5 volts.