2003 5.4 no start, PCM issue?

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BKP83

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2003 Expedition 5.4.

Daughter was driving to the gas station and it just flat out died. She thought she ran it out of fuel. (found out later it still had 1/4 tank) Attendants pushed her to a pump where she filled it up and it still wouldn't start. I grab some tools and rush over to help her out. First things first, I hit the fuel pump reset in the back hatch. No change. I have the fuel pump bypassed already so it's running 24/7 when key is in the "run" position. I hit the fuel rail bleeder and fuel sprays out at alllllllll the volume. She's got fuel getting to the injectors. Still no start so I assume it's got no spark. I hook up my scanner and I get the message, no communication can be established. I've seen this on other vehicles and it's typically a dead PCM/ECM. Security light is quick flashing. No mileage display. Temp displays for about 3 seconds and then blanks out. Had it towed home. I have a spare key that is programmed but never used. I tried it and still same issue. Power is getting to USB so I'm assuming it's getting to the OBD2 connection. I checked for ground at the PCM and it's good. Battery was all good until trying to start it 457 times. She rolls over great, but doesn't fire off. With the flashing light I think I have a PATs issue but why would it just die while driving?

So I'm asking the experts. All signs for me are pointing at a bad PCM or PATs. Thoughts?
 

Hamfisted

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Is the security LED flashing high speed when you try to start it ? That would indicate a PATs problem. Like it doesn't recognize the key. Pop the hood and move the PCM harness around and look for a loose wire in the harness, especially the red one that powers the PCM. Why did you hotwire the fuel pump in the first place ?







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BKP83

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Fuel pump was hot wired by the previous owner. I'm assuming for the fuse box relay failing. It's been fine for 30k so no cares on my part. I did check the PCM wiring and couldn't find a broken wire (i didn't pull apart the loom to be fair). I disconnected all three plugs and checked for the normal signs of failure. Looked beautiful in there.

The quick flash security light is what leads me to the PATs system but why wouldn't the 2nd key work? This is why I'm thinking the chip reader may have failed but that leads to the why did it fail WHILE DRIVING. Never seen an immobilizer stop a vehicle while driving for 15+ minutes.

When I get home I will triple check the one red wire going to the PCM. I've got a great test probe so that should be an easy check. I'm gonna check the fuse box when I get home as well. I didn't realize those things were as finnicky as they are.
 
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BKP83

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Update. it's fixed. One of the girls must have kicked the PCM relay and knocked it out. I got my first chance to dive into it yesterday and found the relay loose in the panel. Plugged it back in and she fired right up.
 

BigOleFordFan

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I had some similar issues with my 011 EL Limited....

It took 3 months & $3K worth of diagnostics and replacing the ignition switch, both keys, several wiring harnesses, the HALO sensor, and some other minor stuff, the 3rd ford dealer I took it to finally solved it....it was the "run/start relay" that was fried....

Since then, all is well, thankfully....I was about ready to give up :)
 
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