**Updated Title: Alarm system malfunction

Just a heads up for anyone thinking about purchasing a used Ford
,circa 2001, that has this anti theft system installed.

Truck: F150 extended cab, 4x4, 5.4L, automatic, mileage is about
198k+. I only have one legitimate Ford key for it.

I have owned this for just under 3 years now. It is basically stock.
Not used for off roading etc. Just your average F150. No performance
mods on it at all.

Up until a month or so ago, it had been starting just fine. No starting
issues ever.

Go to lunch one day, come out, unlock with remote, start, and the
engine dies about 3 seconds later. Not able to restart. No power to
anything, lights, radio etc. Hmmm.

So I disconnect the negative cable for a few minutes and hook it
back up. Power returns to interior. Able to restart and drive on
off.

Does the exact same thing over the next couple of weeks. Happens
randomly. Never know when it will happen.

Someone mentions they had the same issue and it was from another RF
key on the keychain causing interference or a sending a invalid
signal. So I get rid of all keys except the Ford one. All was fine
for a day or so and then it happens again. So that theory goes out
the window.

The one time it happened, it started and stayed running. So I pull
out and am at the traffic light a short distance away just waiting
for the light to change and BAM, engine quits. This was within 2 minutes of starting it. So once again, do the
battery disconnect reconnect and get it going and move on.

Next time it does it, it happens in the driveway. This time the
battery disconnect doesn't do anything no matter how long I leave it
disconnected. So had it towed to Ford dealer.

They supposedly
"reset" the anti theft, and replaced the one battery cable end with
a smaller one that fit better.

I am not feeling great confidence in the vehicle at that point. So I
drive it and wait and see. Sure enough, happens again.

This time I do some additional searching online. And someone
mentions the Xpresskit starter bypass unit and that it can be hooked
up even if you do not have a remote starter. So I grab the Ford
version off Ebay. About $30 bucks.

I had to write the Canadian company a few times regarding the wiring of it.

The brown wire on the bypass unit is normally connected to the remote start
brainbox. But since I did not have a remote start, they said the
brown wire needs to pick up a negative signal when the key is
inserted, in order to activate the bypass. Hmmmmm

The best I can determine, is that the 4 pin PATS connector which is
under the dash, has pin 1 as the ground connection. Whether that
connection becomes live when the key is inserted, I don't know. So I
hook up into that and connect up the remaining wires as per their
diagram. Basically 3 more wires go to the PATS connector and then a
power wire and chassis ground.

The theory is that when the key is put in, it activates the bypass
box and the anti theft does not come into play.

All was fine for about 7 starts. Then today I wanted to run some
errands and went to start it. Same deal, engine dies about 3 seconds
after startup. Greeeeat. This time battery disconnect does not do
anything to restore power. #@$%$##!

So now I am back to troubleshooting this AGAIN.

An anti theft system that shuts out a legitimate key start is completely useless and has major design flaws.

To summarize:

2001 F150 4x4, auto, 5.4L
Bought used. Have had it almost 3 years.
About 198k miles.
Stock truck
Ran and started fine until a month or so back. Now randomly will
kill the engine within 3 seconds of starting. No restart ever able
to be accomplished without battery disconnect/reconnect.
Even that now has failed to reset it a few times.
Istalled Xpresskit remote starter bypass(keyless version).
Problem persists.

I want to take this anti theft system and rip it all out of the
truck, and send it back to Ford HQ engineering with a note to let
them know how much I enjoyed having it on the vehicle.

Does anyone have a solution for this, other than replacing the
engine with a 1960s V8?

I am out of ideas and the dealer is pretty much clueless.