Conditions for Setting the DTC

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

The PCM detects a temperature difference between the ECT sensor and the IAT sensor of more than 100° C (180° F) at start up.
OR
The PCM detects a temperature difference between the ECT sensor and the IAT sensor of more than 15° C (27° F). The vehicle must then be driven for 5 minutes over 40 km/h (25 mph). If the IAT sensor temperature decreases more than 5° C (9° F), an engine block heater was detected and the test is aborted. If the IAT sensor temperature does not decrease, an engine block heater was not detected and DTC P0116 will set.