Which one? The digital one is on the front of the block under the fuel rail. The analog one (the one used for the dash), is on the back of the block somewhere.
It is front of and to the left of the passenger side fuel rail if one is looking into the engine bay. I had to take off the fuel pipe jumper to get it out though. Make sure to use new crush gaskets for the fuel union bolts. Torque fuel union bolts to 25ft/lbs using a 17mm crows foot. Torque new ECT sensor to 14ft/lbs using a 19mm socket.