Gidday Walter
Some of the newer OBDC II code readers have provision for remote sensing of things such as oil and water temperature. If I were to use one of these, I would attach the sensor unit to the bottom of the cooling system somewhere. This is usually the last part to run out of water, so gives a much better idea of what the coolant temperature actually is.
According to the Haynes manual, the Engine Coolant Temperature (ECT) is in two different places, depending on the model year.
For 2000-2004 N/A engines, it's located under the right rear intake manifold for cylinder number 3. It's screwed into the coolant passage that's bolted to the top of the block.
For 2005 turbo and 2006 N/A models, the ECT is located on top of the engine block, under the right side of the alternator.
Hope this helps. I have no idea as to its accuracy ...
