Looks like another case of the MAF signal return is bad internal to the PCM. To the best of my knowledge that's where everything is tied together before getting tied to G101 on PCM Pins 40 and 60. This is the same convention used for the other sensors that use Signal Return. With an open return circuit your DVM may be picking up stray voltage. You can test that theory with an old school test lamp. Just like the DVM test attach one side of the test lamp to the positive battery terminal. Then probe Pin C of the MAF meter. With a true open circuit the bulb will not light.

If that is the case, a test would be to run a temporary jumper from MAF Pin 3 to ground (Pin B since it is a direct path) to see if the MAF test works and the code goes away.

 

Some interesting stuff in this video including testing the actual circuits. some of the tests require obdII, though

 

Just to come back and close this out for all that may find this thread;

Unfortunately there's not much to update in the way of what seemed to be a short in the ground wire going from the MAF sensor to the ECM. The original problem was getting 12 volts to the 2nd pin/wire from the left instead of 6 as per one of the "easyautodiagnostics" articles linked by rla2005. After getting hung up on the issue for a while and being unable to trace the source of the short(a good opportunity to invest in one of those short circuit locator gadgets), I took it to a shop which couldn't quite pinpoint it either, but defaulted to redoing the connector harness that I did and swapping yet another MAF sensor for an OEM quality one(not like the Walker one I had installed a month or two prior). Well, they asked for a bit more than I was willing to spend, and I took the truck home, and bought a whole MAF sensor assembly, tin can and all, off eBay. Supposedly off a barely driven '95 E-150 with the 5.0.

Welp, changed the sensor assembly for the motorcraft one. No codes since, no rough running, stalling, or transmission cutting in and out. Really should have know better to go with OEM all the time, but parts are increasingly sparse and I've had no problem with some other aftermarket applications...yet. The thing that bugs me is that after I got it home from the mechanic's, that pin was showing 12 volts! I have no clue what they messed with but I'm glad it's put to bed. My soldered connecter harness is doing just fine to date.

Now to go get a new catalytic converter welded on after many months of running an incorrect fuel trim... the fun never ends!