I think I've determined my root cause but I need a way to track down stray voltage.

I'm getting 11.5v on the purple wire of the CAN bus. This is CAN bus wire #3. I found a site that shows it plugs into what are labeld as UBP at "Drivers Seat Module", "Security Module" and "Temp Module".

Drivers seat module is obviously under the drivers seat
Security module is on the back wall behind the seat back
I have not located Temp Module yet, but I'm guessing it plugs into my climate control.

Any help would be greatly appreciated.

FYI this is the site I am referring to above:
http://www.automotivetroubleshooting..._protocol.html

 

There are three significant errors in that diagram and writeup.

1. The UBP wire is a violet wire, not yellow.
2. The The UBP bus goes from the DLC to a splice, then there are four wires that go to each of the following: EATC, BSM (aka VSM), Inctrument Cluster, and Driver Seat module (if equipped with memory seats).
3. According to the factory manual, that line is supposed to be +12 volts whenever that bus is inactive.

What actual problem with the truck are you trying to solve? It sounds like you may have wandered off in the weeds beyond the outfield.

 

I can not argue with anything you said above, especially the part about the weeds. I typed out a long version a few posts down https://www.f150online.com/forums/20...ter-floor.html, but the short verson:

- No crank, no start, no codes.
- When it's failing my code scanner is unable to connect
- Unplugging the battery for upwards of 5 minutes usually resets it and I can then drive the truck for anywhere from 10 seconds to all day.
- When it fails again, sometimes after it's been sitting (aka shut it off for the night, try to start up the next morning and nothing), sometimes while I'm driving or idling.
- At a couple points I did see codes P060B and P2107

Checking the fuse box, I found the carpet on the passenger floor board was pretty wet so I eventually discovered a significant cut in the rubber molding where the harness comes through the wall in front of the door. Directly behind the fuse box. I've sealed this hole now, so no new water will be coming in that way. I also pulled the whole fuse box out and took it apart looking for corrosion but found none. Put everything back in using di-electric grease on all connections.

Where is that "splice" you speak of?

FYI, mine is 2006. I though I setup a sig line, stupid me. The reason I'm asking is because of the site I listed above saying I should have 7v on #3. I had figured out that it's the purple aka PPL wire. I have 11.5 to 11.9, usually 11.5 though at KOEO. I started pulling fuses looking for a a change and thought I was onto something when I pulled the fuse for the power door locks and it dropped to something like 9v (it was getting late). But when I pulled fuse #5 the voltage dropped to a solid 5.9v.

 

The 06 is the same as the 05. That article is simply wrong on all three issues as far as I can tell from the manual.

That most often means the PCM isn't getting its operating power. Just an observation.

It doesn't matter, it's not the issue.

F5 supplies constant power to the PCM and the EATC, probably for keep alive power functions. If the fuse is out, the voltage on the UBP bus is probably invalid.

 

Any recommendations on where I should be looking?

 

Look for the PCM to be powered up every time first. If it doesn't power up, nothing will work. If it powers up only intermittently, then the whole system will be intermittent. A good indication of PCM power-up is usually if the MIL comes on at key-on (before start).