ECT 2
WARNING: This page is about a different car, the 2011 Jaguar XK and 2010 Jaguar XK. However, it is still accessible from the selected car via links, so may be relevant.
ECT 2 is installed in the lower hose connector which attaches to the bottom of the thermostat. The input from this sensor is used for on-board diagnostic (OBD) 2 diagnostics and, in conjunction with the input from ECT 1, to confirm that the thermostat is functional.