The "Check Charging System" warning that won't go away...

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bgrattan

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(2006 Expedition, 194K miles)
A few months ago, I got my first "Check Charging System" error. It would come on intermittently, and go away when the engine revved up.
I took the alternator to the shop, surprisingly, it tested "OK."
The problem went away for a while. Recently it came back, only worse. I had bought a voltage meter that plugs into the cigarette lighter, so I could tell the battery was not getting charged at times (was sitting around 12V and then going lower).
Finally, on a long drive, it did us in and the battery got so low that the Expy died. The next day, I got a rebuilt alternator. Installed it without issues.
Fired up the Expy, the battery is charging no problem, but the "Check Charging System" still comes on. I look at the voltmeter, it is reading 13.4. I figure all the deep discharging damaged the battery.
I got a new one. Fine, now it charges to 14.2. "Check Charging System" now comes on every time I start the engine after it runs for approximately 15 seconds. However... the battery is staying charged at about 14V and when I measure the current from the alternator it is about 25A. When I switch on the lights, it jumps to 34A. It seems like everything is in fact working, but I'm still getting the "Check Charging System."
I borrowed the scanner from O'Reilly's and it only told me that I got error P0622-FF which isn't very specific as far as I can tell.

How risky is it to take the Expedition for a long drive tomorrow, and do you have any recommendations for figuring out what the root cause is?

Photos of scanner results here:
https://www.dropbox.com/s/4y4t7ax4wbcmk32/Photo Jul 29, 7 23 23 PM.jpg?dl=0
https://www.dropbox.com/s/tuk6s85ttnk5b1o/Photo Jul 29, 7 23 35 PM.jpg?dl=0
https://www.dropbox.com/s/irzfep2fn7vvirv/Photo Jul 29, 7 26 34 PM.jpg?dl=0
 

thesavo

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I would check high current cables for green custy (corrosion). You replaced the alternator already, and one would presume the battery isn't that old.

Check the alternator-to-battery. Battery-to-body, battery-to-engine block, and battery-to-starter.

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thesavo

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Could be as simple as leaving off the comm harness to the alternator, or corrosion on connector terminals/wires

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Jeff G

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When I had that issue, it turned out one of the plug connectors at the top of the fuse box wasn't seated all the way in. I too replaced the battery, alternator and even the PCM before I found the connector loose and not seated. I had all the same symptoms you described.
 
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bgrattan

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When I had that issue, it turned out one of the plug connectors at the top of the fuse box wasn't seated all the way in. I too replaced the battery, alternator and even the PCM before I found the connector loose and not seated. I had all the same symptoms you described.
Where is that fuse box? It isn't the one by the foot of the passenger side door is it?
 

Jeff G

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That's the one. There are several plug in connectors at the top. I didn't see it at first and only found it by accident when I checked them all for tightness and it went "click".
 
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