Engine Coolant Indicators

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

The instrument panel cluster (IPC) shows the engine temperature on the temperature gauge. The value is sent on the data communication line from engine control module (ECM). When the coolant temperature is more than 132°C (270°F) IPC receives a discrete input from ECM requesting illumination.
The IPC performs the display test at the start of each ignition cycle. The IPC illuminates the TEMP indicator.