Prices
Ok I know a bit on this subject, the $100+ tag is (was) holdens price for the VS coolant temp sensor they changed it because of a flurry of complaits molsty from people who noticed that other moldels and V8 types were $17 that were made of the same components and I`d say (guess) that not all dealerships got that memo.
Now a thing to do when you get that code that won`t cost you a cent is clean the earth wire that earths on the block with a wire brush.
its located on the drivers side of the engine half way down the front on a stud clearly visible next to one of the heater hose outlets this solved my problem and I am getting great fuel economy from my GF`s VS.
hope this helps
In this link it will show the location of the two common earth wire shared by the CTS TPS and oxygen sensor on the VR buick (they stuffed up saying the pick was a VS) these are the ones responsable.
Injectronics Automotive Electronics Parts Melbourne Australia - 40) Oxygen Sensors (VS V6 Commodore)