Check Coolant Temp
WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The IPC illuminates the CHECK COOLANT TEMP indicator in the message center when the IPC determines that the coolant temperature is greater than 121°C (249.8°F). The IPC receives a class 2 message from the PCM indicating the coolant temperature.