Conditions for Setting the DTC: P0128
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The ECM detects that the minimum ECT of 55°C (131°F) has not been met with a start-up IAT of less than 10°C (50°F).
OR
The ECM detects that the minimum ECT of 80°C (176°F) has not been met with a start-up IAT of greater than 10°C (50°F).