DTC P0116: ECT Sensor Performance: Description
WARNING: This page is about a different car, the 2002 Saturn LW200, 2002 Saturn L200, and 2002 Saturn L100. However, it is still accessible from the selected car via links, so may be relevant.
PCM compares Intake Air Temperature (IAT) sensor reading to Engine Coolant Temperature (ECT) sensor reading to determine accuracy of ECT sensor. DTC P0116 sets when IAT and ECT are not within a calibrated range after a period of time after the ignition is turned off.