I have a 98 Camry and the fans stopped working. I am assuming the ECT switch is bad. At the same time, the engine sometimes dies on me or idles roughly. I am getting a P0115 error code which says the ECT sensor is bad. Do I need to replace both? It says a bad ECT sensor with cause the engine to sometimes die, but does the ECT sensor control when the fans come on?? Then what is the ECT switch for?? I guess I can just replace both.

On many cars, the ECT Sensor is a thermistor which controls the air/fuel mixture and provides data to the PCM for turning on and off the radiator fan. When the engine is cold, the ECT Sensor provides a richer fuel/air mixture; when the engine warms up, it provides a leaner mixture. On your car, like many Hondas, you have a separate ECT Sensor (2 wires) and ECT Switch (1 wire). Your ECT Switch controls when the radiator fan goes on and off. Both are easy fixes. They tend to fail, when you don't change the coolant regularly (every 2 years) with a 50/50 mixture of the recommended antifreeze and distilled water.