What is a low CoolanT Indicator? LCI? What does it do? How to attach it?

What is a low Coolant Indicator?
A low coolant indicator sensor passes a signal to your dash indicating when your vehicle is low on coolant.  The LCI port is usually located on the passenger side of the radiator, halfway down the header tank.

What does it do?
If you have a low coolant indicator light up in your vehicle, it usually means you need to add antifreeze. This can be done easily through the overfill tank underneath the hood of the car. Carefully add a mixture of antifreeze and water to the overflow tank until it reaches the full mark. Antifreeze and water are usually mixed in equal parts

How to attach?
If you order a radiator with a sensor port.  It will come plugged.  The plug can be removed.
The plug is installed and locked in place with clips located on either side of the plug.  Included below is a picture of the sensor plug for reference.