I was driving my 2002 screw to work th is morning. Had the cruise on and all of a sudden the truck just shut down and wouldn't start back up and the theft light was flashing. What could cause this???

 

PCM relay under the hood

 

I replaced my pcm relay shortly after the first post amd it still just randomly dies on me and the theft light is blinking and the odometer reads ------ and it takes me a while before it will start again. Today I went to put my key in ignition and halfway in the ignition it let me turn ot to try and start it. Could my key amd ignition cylinder be at fault or the actual ignition switch itself? ?

 

Ahhh... the dreaded PATS issue. This is definitely sounding like one.

 

The cyclinder is mechanical it should always allow you to turn it. The proper key and a good ignition cyclinder will always allow the starter to turn over, just not let it start. The pats system, aka the chip in the key tells the PCM its okay to turn on the fuel/injects/ other crap to let the truck crank.

 

Going off what IBD wrote, if there is one issue in the system where all the codes in the key, cluster, and PCM don't align, those injectors won't be turning on anytime soon.

 

It sucks cause I never know when its gonna do it? I had a brand new key made about a month ago amd it still done it so I don't believe its the keys or relay. Maybe a bad pcm? If I got another pcm would I need to get new keys and everything? I LOVE my truck until it does this, then I just wanna burn it to the ground cause I get so frustrated!

 

The transponder/pats for the ignition is within the switch itself. Its really a transponder. This is why cheap aftermarket remote systems just use a coil of wire around the ignition cyclinder and the other part of the wire wraps around your programmed key to tell PATS and the PCM it is okay to start.

If you can use a wrench (with gloves or rubber on it) to touch the two starter relay bolts together and the starter turns over, it is more than likely an ignition problem. Put your key in the ignition with the truck in park, and touch the bolts together. If it doesn't start then you have PCM or other issues. If it does start, its the ignition switch or something inbetween

Think this is what you are needing.
http://www.oreillyauto.com/site/c/de...3701&ppt=C0329

 

This may help some.
https://www.f150forum.com/f75/remote...er-how-200542/

 

IBD, by transponder do you mean the transceiver? that circular part behind the ignition? cause thats one of the main issues when it comes to the pats even with newer vehicles.