Thanks, mine is a 4.4 - so it is a different style; but it also came in a housing. I probably should have added that the code is thrown ~5 seconds after starting the engine; and the vehicle warms up quickly as it should - so I am confident it is an electronic issue. Mechanically the thermostat seems fine. But clear the code, shut the engine down, restart, count to five and here comes the CEL.

The questions is if it is an electronic issue with the thermostat or elsewhere. Testing with a meter across the Tstat shows continuity - I would think that is correct as I would expect a failed heating element to show open.

8V at the connector seems a bit odd to me; I don't know if the voltage should vary based on temp or if it is an on/off situation. If the latter, I would expect to see 14v or so.

Ugh - fun stuff.