Coolant Temperature Sensor
WARNING: This page is about a different car, the 1999 Cadillac Eldorado and 1999 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
The coolant temperature sensor is located in a coolant passage of the intake manifold. Sensor output is monitored by the PCM, which in turn sends a signal to the ACM for system operation calculations.