Thanks. I'm just sort of confused how one sensor can say temp is too low, while the other says everything is fine. Could it be a bad sensor vs. a stuck thermostat?

 

Exactly! That's the nice thing of having 2 separate monitors. The diversion tells you something is wrong with the ECT sensor or its circuit.

And this gives me an opportunity to expand on my epigram!
The dash gauge is not very accurate, in fact mine only gives a read out in "cold-normal-hot". However it may be precise as in going to the same spot every time it hits a certain temperature.
The ECT sensor for the pcm feed should be more accurate and more precise as the computer will use the data to calculate a few things.

So most likely the Enging Coolant Temperature sensor is malfunctioning. Check the wires and harnesses, take out the sensor and see if its surface has been gunked up or go ahead and replace it no questions asked. Change the engine coolant and the thermostat at the same time. Don't use cheap parts.

 

We just went full circle!
Refer back to post 3 and 4 1st page!

 

With almost 130K miles, thermostat is probably due for a change anyway. I was avoiding it as it's not nearly as accessible as the one on my truck was.. Of course the light has been off for the last 3 days, lulling me into a false sense of security.

 

You can test a thermostat on the stove. Google for how to do it.

I replaced the thermostat on my wife's Contour without testing it. Then I found there was a leak in the system. So I wasted the money for the thermostat and then I used leak stop and it's ok. now.

If you do replace the thermostat get a good quality one. Stay away form the cheap parts.

 

That's definitely a good tip. The annoying part is that pulling it just to test requires draining the coolant system and pulling the belts. Not looking forward to it. Last time I changed a thermostat it was was right up top (v6 truck), not buried in the bottom of the engine compartment. I'll give it a shot.