2 wire sensor ok , but if ECM is bad why would fans come on when I disconnect the coolant sensor plug? And when I jump the fan relays?coolant sensor 1 or 2 wire? if its 1 wire, the body has to be grounded for it to work. another option is a faulty ECM, this may be why they jumped the fan in the first place.
Understand thanks so much. I bought a new cts and installed it nothing Happened still fans did not come on removed cts and did a ohms test and got a reading of 2.00 ohms on the sensor now, I removed the cts again this time I plug the cts to the harness and with cigarette lighter I heated the tip of the sensor thinking it would turn fans on, nothing! Now, I took the old cts did an ohms test (200 scale ) and the reading was 1.50 ohms and then heated the tip on the cts and to my surprise the fans came on. The only thing I noticed was the both CTS are of different colors the original is brown and the new one (the one did not work) was black I assume that have different ohms value also, I cleaned the pins that are inside the old cts.Jumping fan relays will turn fans on, you are effectively bypassing them.
As to why the fan comes on with the sensor unplugged, the ecm will be detecting an open circuit on the sensor and going to a safe condition which is to turn fans on.
The sense side for temperature turn on could still be faulty in the ecm however. Further investigation is required to find the exact resistance that will make the ecm trigger the fans, then see what temperature that corresponds to at the sensor.