Sometimes coolant fan stays on after engine is turned off...ambient temperature could be as low as -8 F. or in the 20sor 30s. Noticed that sometimes the temperature gauge goes to min. Before this happens, engine RPM reduces slightly and the coolant fan comes on. I thought that the fan running in the severe cold was reducing the engine temp, so I unplugged the power at the fan relay, and the temp still went to min on the gauge and then to normal...randomly. I changed the thermostat before I observed all this and everything appeared normal for about 5 minutes and then the fan came on and the gauge went to min, the RPM reduced and several minutes later the temp went back to normal. I get an error code of "FAN 2 CONTROL CIRCUIT; PO 481 $7A". When the temp goes down on the gauge, it goes down very quickly...almost like the temp sensor is unplugged. I think the fan stays on when the engine turns of, the temp gauge is either correct or at min, or this event ...the fan coming on or going off appears randomly. Also, after the ignition is turned off, if the fan stays on, it does time out and turn off. This is my wife's car and I only got to observe for a short time yesterday on our warmest day this week w/ temp at 22 F. These symptoms appeared with the severe cold weather and after I washed the car during a spell when the temp went above freezing for a day a few weeks ago.