Temp Gauge Problem???

This is for a 2001 Chevy Venture LT with 60,000 Miles.
Here is what I know about the problem:
1) Temp Gauge sometimes acts normal, but at other times it doesn't move at all from the time I start the car, driving in city or highway, etc. It remains well below the bottom line.
2) Heater works fine as if the engine is warming up fine.
3) No coolant smell in heater.
4) Service Engine Soon light came on, with code "Coolant Temp reading out of range" according to Autozone. Had the coolant temp sensor replaced but this has not had an impact on the problem...my mechanic said it could be a computer problem that I would have to go to the Chevy dealer for.

Any ideas? I appreciate your input!

my 98 act the same way too as if the thermostat stuck open. since the thermostat is difficult to get I just leave it like that. my check engine light don't come on and I still get heat in the vehicle in the winter. I heard other people coplain about the same problem

Another thing that is happening...the radiator fans kick in as soon as I start the engine as if it is hot; although it is 20-30 Degrees outside. If the Thermostat is stuck open I would expect for the heater to not be working well. Also, the thermostat is not hooked up to any sensor so there has got to be a problem somewhere that is telling the temp gauge to read abnormal temperatures and for the radiator fans to run constantly?

The reason that your radiator fans start up when you start your engine MAY be from having your heating controls set to defrost. The defrost setting starts the air conditioning compressor. This requires the cooling fans to run to cool the condenser so that a high head pressure compressor condition does not occur.

My temperature gauge in the dash rarely goes above 1/4 sweep. I wish that it would sit at mid-sweep at normal operating temp.

For these vans, quarter temp on the guage is NORMAL. I would be concerned if the gauge was creeping up to half without the fans kickin on and bringing it back down. only time my temp guage would jump up to half was when sitting in traffic after coming to a stop after highway driving with air conditioning on. And this was cured after leaky intake manifold gasket was replaced. You could have some clogged coolant passageways in the motor, have you had your intake gaskets replaced on your van yet? It really does sound electrical though, and my first thought was the temp sensor, maybe the new one is not connected or working properly? They should be able to test the sensor with a multimeter or take it back and get it replaced again (should be free if this one aint working).

Thanks for the input. I have not yet had the intake gaskets replaced...how expensive is that? I would love it if my gauge would read 1/4...but it just sits in the same spot as it does with the engine off (although it does move slightly when I start the car indicating that it is getting power), and then it stays in the same location while we are driving regardless of driving conditions. I have noticed that we might be losing a little oil now too...does this sound like the intake gasket issue? We bought the van used about 10 months ago with 55,000 miles on it and have put too much money into it already...if it needs intake gaskets I'm trading it in for something the General DIDN'T make.

Had this fixed over the weekend. Had sludge in the coolant so had to flush the coolant system, refill with fresh coolant...also replaced the thermostat. Running fine now.