Engine Coolant Temperature
WARNING: This page is about a different car, the 2002 Chevrolet Malibu. However, it is still accessible from the selected car via links, so may be relevant.
The IPC illuminates the engine coolant temperature indicator when the body control module (BCM) determines that the coolant temperature is greater than 123°C (253°F). The BCM receives a class 2 message from the PCM indicating the coolant temperature. The BCM sends a message to the IPC via the serial peripheral interface (SPI) requesting illumination.