(Engine Coolant Temperature) Sensor. This guide explains how to test the sensor using a multimeter to ensure it is sending the correct signals to the vehicle's computer (ECU). Here is a breakdown of the technical details presented in the image: 1. What is an NTC Sensor? The image highlights that this is a "Sensor with negative temperature coefficient" (NTC). The Rule: As the temperature increases, the electrical resistance decreases. The Result: Because the resistance drops as the engine heats u