Located on the bottom left side of the radiator, next to the lower hose. There are several sensors on the 1.5 liter. The engine coolant temperature sensor you're referring to (I think) is located in the intake manifold, at the left hand side of the head. I always get the guage sender and this coolant sensor confused, they are adjacent to each other. Unplug one then check your guage when engine is hot, this will cause the guage to fail to register a temp, and you can identify the proper sensor.
Engine Coolant Temperature Circuit High Input The engine coolant temperature (ECT) sensor is a thermistor screwed into a coolant passage in the cylinder head. Sensor resistance is high when coolant temperature is low and resistance drops when coolant temperature increases. The powertrain control module (PCM) provides a 5 volt reference and a ground to the sensor. The PCM monitors voltage drop to determine coolant temperature. If the ECT reads less than freezing temp. when engine has been running for more than a few minutes, the PCM determines a circuit fault and sets this code. Or if the PCM determines the sensor resistance is out of specs, this code is set.
coolant temperature sensor is the right of the coolant outlet line on the top of the engine when looking at while standing in front of the truck. it has a black two prong clip attached to the sensor. the oil temp switch is to the left of the coolant outlet line. it has a single black wire coming off of it.