Action Taken When the DTC Sets

WARNING: This page is about a different car, the 2017 GMC Acadia. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0128 is a Type B DTC.
The engine coolant temperature gauge defaults to cold.
The A/C is commanded OFF and inoperative.
The cooling fans are commanded ON.
The Driver Information Center (DIC) may indicate a steering assist reduced message.