Just curious... If it's a 1 wire temp sender, does it have a good ground?. I know it's threaded into the engine block, but maybe the threads are dirty... What happens if you hook up a resistor of the appropriate specs to tell the ECU that the engine is warm?
Of course, if it's a two-wire sensor, that all goes out the window. Sorry I don't remember off the top of my head which it is. Does a check with a multimeter indicate a short in the wiring to the WT sensor? If no short, what happens if you bypass those wires entirely?
Keep on muddling foreward. At the worst, you can replace the whole thing one part at a time and then you'll have a brand new truck for the next 30 years.
