Thanks, guys! I'll have him pull the connector on the front radiator mount to check for corrosion. Based upon what I've read, it sounds like this isn't an uncommon problem. But, those who seem to have noted that this sensor was either bad, had a broken pin, or was corroded seem to report the 4-2 flash; not the 2-4.
Any Ford Techs know how to decipher this 'mystery code' for the 2004 F-150?