I have a 2002 f150 and my theft light is on steady. It used to be an intermittent thing and only come on steady once in a while but now it is always on. Truck starts fine, but I am worried it may stop starting fine. Any ideas what I can check before carrying it to dealer. I have tried both of my keys and have the same problem with both. Even with truck turned off the light is on steady.

 

This would indicate a PATS system fault. You'll have to look for codes (Probably a b1600, 10601, 1602, etc) and chase from there.