Hot Coolant Temp
WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
The IPC illuminates the hot coolant temp indicator in the message center when the PCM determines that the coolant temperature is greater than 128°C (262°F). The IPC receives a class 2 message from the PCM requesting illumination.
The IPC sends a class 2 message to the radio in order to activate an audible warning.