Coolant Temperature Sensor
WARNING: This page is about a different car, the 1987 Toyota Cressida. However, it is still accessible from the selected car via links, so may be relevant.
The coolant (water) temperature sensor is installed in intake manifold. This sensor is a thermistor which converts temperature of engine coolant to electrical signal for use by ECU. The ECU uses coolant temperature information for controlling fuel injection duration, spark advance system, idle speed control system and EGR system.