Yep CTS>coolent temp sensor three wires,guage ,computer,id,s light......check block temp
Confirm your block temp first.....check for break in id light wire......if temp doesn't match sensor is faulty.....should run bad if sensor is bad computer gets wrong temp info
I have the same problem with the water in fuel light, have tried everything and can't get it to go out!
Having said that, check out this thread at powerstrokenation.com
Eng. Temp. light came on but... - PowerStrokeNation : Ford Powerstroke Diesel Forum
Talking about the exact same thing with a couple of pictures for sensor location.