I've got a 2000 F-150 Supercab 4.6L auto 2WD. I've seen a few posts about the anti-theft light in these trucks, but none seem to address the issue I have. This morning I drove my truck to the gas station, parked, shut if off and went inside. When I came back out and started the truck back up, the anti-theft light was blinking quickly after the truck was running (something I know it's not supposed to do). The truck was running fine and nothing seemed to be wrong, so I watched it as I pull out and began to drive down the street. The blinking slowed until it would blink once, pause, and then blink six times. It continued this pattern for about 5 minutes before the light finally went off. While the truck was running it never came back on, but I haven't started my truck again since the gas station. I have a trouble code reader, if that would reveal anything. I should also mention that for the past 2 or 3 weeks the guages have been randomly resetting (like the battery has been disconnected) when I start the truck, but the engine turns over fine and it fires right up with no problems. The only after market device I've hooked up is a stereo amp that is wired to the positive terminal on the battery, but I've not had any problems with it, unless they are starting to crop up now (after 6 months). Any help would be great!

 

Just a little update. I went out a few minutes ago to see if the theft light was still doing the same thing and also to see if the truck would even start. When I went out, the theft light was not blinking at all (like it normally does when the truck is just sitting and not running). The keyless locks still work and the panic button still works. I got in the truck and turned the key from off to run and the gauges lit up like normal (including the theft light which went off after a few seconds). I turned the key to start and the truck fired up and started just fine, with no blinking theft light. I popped the hood to check the battery connections and they are tight. I got back in the truck and shut it off and removed the key. The theft light was blinking like normal again (when the truck was off and sitting). I put the key back in and turned it to run and all the gauges pegged and went to normal like they've been doing intermittently for a while now. I turned the key to start and, again, the truck started up and ran fine, no blinking theft light and no wierdness. I'm starting to think it might be the battery or possibly the alternator, but it's also possible that it could be a million other things. Hopefully whatever it is it will be cheap because I'm broke. Thanks in advance.

 

Sounds like the battery. Take the battery to the parts store and have them check it. The electronics are very sensitive to voltage drop.

 

That's what I was beginning to think. I've read a few posts with people talking about the theft light flashing the same way mine was, but their trucks either wouldn't start or shut off soon after starting, but mine ran fine. Of course, I just drove 50 miles about 10 minutes ago and the light never flashed, so maybe it was just a gremlin that cropped up and went away. Either way, I will probably get a new battery because I know this one is old and has a lot of miles on it. Thanks for the reply.

 

Possibly ignition key cylinder?!? I have 04, have the original keys, but every once in a while, I'll go to start truck and it will crank and Frank until the battery dies. Took me a couple fuel filter replacements till I realized it was the anti theft system... Sometimes it thinks I have a shaved key, out whatever it is those machines think... Pop out the key, re-insert fully and no more problems...
just a thought... Don't know about what..I forget... Did I mention I'm blonde?