With my 2000 echo when you start it a blue temp gauge looking like a thermometer shows when car warms up it goes out indicating it is warmed up....If the red one comes on after driving for a while it is telling you car is overheating very simple but very effective once you know this

Most likely the wire is lose under the hood - check that - end of problem - most likely - if the wire looks ok - still remove and put it back - just to tickle it a little -