2000 Ford F-150

Steering problem
2000 Ford F150 V8 Four Wheel Drive Automatic 74000 miles

The truck seemed to be fine, I stopped for about 5 minutes with the truck running and in park. I backed out of the drive way turning left and when I put it in drive I lost the power steering. I drove home but it was very difficult to turn, almost impossible. The power steering fluid is between the Min & Max line. The weather is very cold it was approximately 10* when this happened, but this was after I drove more than 20 miles. Where should I start looking? Is there a way to troubleshoot the Power Steering Pump?
January 2, 2008.

Start with fluid if all OK and no leak
check the pump

ive had some pumps fail s under very cool weather
you can remove hose and check for pressure
most likely you need to replace the pump

good luck

Jan 2, 2008.