The sensor (mounted on the inlet / outlet header), is done. You will need to replace it. Thats the way it has been, for me.

Now, i suppose that the plug (on th circuit board), could go bad, I just haven't ever seen it. I have changed maybe 10, over the years. A very reliable sensor IMO.

Note: There may be a chart in your owners manual that will list various resistances to temperature, if you wanted to test the sensor with an ohm meter.

Did that make any sense?