That reading would tell the computer that the temperature is about 68 degrees. Is that correct?
I went through the entire wiring diagram for the truck and white - red is a 12 volt wire with then key on that goes all over the engine compartment. Yellow is used on a couple of different circuits, the throttle position sensor, the alternator (sends the signal to the dash warning light), from the cruise control computer to the relay, and from the little square check connector under the hood to the computer.
I couldn't find anything with both the yellow wire and a white - red wire.
So now we know that the solenoid works and the ECU works. So it still comes down to inputs or to the ECU or a faulty ECU.
The thing to check now is to back probe the ECU and see if you are getting the same readings at the ECU as at the sensor. If not, there is a broken wire between the sensor and the ECU, or a bad connection at the ECU. Using the same color code of the wires, check resistance at the back of the ECU.
The most common cause of a problem is with the connectors at the back of the ECU. If you have to rock the connector to get it disconnected from the ECU, it's common to stretch the connectors out and cause an open circuit. I use a piece of piano wire to test the tension on the connectors. Be gentle, it's really easy to stretch out a connector with too big of a piece of wire.