Conditions for Setting the DTC: P1115
WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.
The control module detects that the ECT sensor parameter is less than -37°C (-35°F) intermittently for more than 20 seconds.