What is the sensor called on the thermostat housing

Part of the issue may be that I only show the engine option as a 3.5L. You said your engine is a 2.9L. Is this accurate?

I have included the location for the ECT sensor. If you look at the second screen shot, you will see I put a box around the ECT sensor. The line that appears you are referring too is most likely a bypass hose in the even the thermostat is stuck.

Can you get a picture a little further back and we will see if we can locate your sensor assuming this is the same engine. Thanks

Which engine do you have? 2.9L or the 3.5L?

So that is the issue. That is the coolant sensor but I too cannot find a diagram on it. We don't have a manual on it because we don't have the 2.9L diesel here in the USA. Plus I didn't notice the engine cover in the picture you took where it clearly labels the engine.

If you want to confirm this and you have a code reader, just unplug the sensor and you should set a code for the coolant temperature.

Sorry I don't have any detail on it but that is what the temp sensors look like and clearly it is in the cooling system.