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

It's the sensor on the thermostat housing I can't work out, I can't find it on any diagrams, the big hose above the sensor runs into the radiator.

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

It's a 2.9.

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.