The Thermosensor is located towards the top of the water pump but on the backside of the pump. It features a plug which looks similar to the BAC plug and injector plugs. Sometimes one of the pins inside the plug gets pushed back and thus doesn't make contact with the Thermosensor such that the ECU doesn't receive the proper signal. One of the best ways to test the sensor is by taking a voltage reading at the ECU w/key to on.