Diagnostic Aids
WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.
Coolant thermostat is stuck open.
High resistance in the circuits of the component may set DTC P0128, P01F0 without setting the DTC for the component: B34 Engine Coolant Temperature Sensor