i have a 2001 2.7t with 122K. The auxiliary fan (radiator cooling fan) will not turn off even wen the car is off. Only way it will shut off is if i disconnect battery or a connector which is located on the drivers side jus a bit behind the headlight.
i read several posts that say it could be cause by water in the plenum chamber ( ecm box) shorting a relay? i checked...no water. Would it be the auxiliary fan control unit that needs to be replaced? if so does the entire front end need to come off? The fan wen on is running really high speed and continues to even wen the engine is off....does not shut off by itself.

 

Water wouldn't still be in there, pull out the relay and look for corrosion.

Keep those battery tray drain holes cleaned out, trust me.