I was poking around in the engine bay of my 1998 Honda Civic LX (Y7 motor) and I noticed that there are a total of 3 connectors plugged into sensors near where the coolant moves around the engine. I looked through the service manual and confirmed my suspicions that they're all related to coolant temperature. One is the coolant temperature sending unit (1 wire) that is for the gauges, one is the ECT (Engine Coolant Temperature Sensor, C122 connector) which tells the ECU the coolant temperature and one is called the ECT (Engine Coolant Temperature Switch, C119 connector). Now the First two connectors are at the front of the engine, off the valve head and the last connector is near the back of the engine, coming off of the thermostat housing.

Now what I'm wondering is, WHAT IS THE Engine Coolant Temperature Switch with the C119 Connector used for??? I can't find any references to it in the service manual aside from it being listed as a component on the engine wiring harness...

 

That is for the fan switch.

 

Thank you very much!!! I finally found the reference in the service manual in regards to this switch, all thanks to you!

 

TW sensor - sends coolant temp to the ECU to help determine fuel/ignition info
Coolant temp sensor - sends signal to the gauge in the cluster
Fan switch - sends power to the fans at predetermined temperatures