Strange Temp Problem

Ok here it goes,
I was driving and the temp gage went to below cold and the fans stayed on. Replaced the temp sensor by the thermostat. The old one was reading open. It worked great for 3 or 4 weeks. Then today coming home it did the same thing. Thinking it was the new sensor gone bad put in a new one and same problem. Checked one side of the sensor wire, it checked ok to ground, the other side checked fine to the PCM.
Now i think that the section of the PCM is bad.
Is there something special about the PCM in the 2001 venture?
If i install a good used one do I have to reprogram anything ?
Does anyone have the part number?

Thanks,
Donnie Lee

Thank goodness for Autozone.
Called the one down the road from me to get a price on the PCM.
The person behind the counter said it was rare for them to go bad and to bring the van by.
Well he hooked up the diag machine and behold there was an error about the coolant temp was lower than the sensor. P1??? something. I forget what code.
They cleared the code and it all started working, The gauge came up fans cut off and its back running.
Don't know what caused the code but its fixed.

Donnie Lee