FYI, I tried a search and came up with nothing. There are 4 wiring harness's on my 93 4 liter, all on the passenger side, and none of them are plugged into anything, and the don't plug into each other, so it makes me curious, are they diagnostic? It seems like a bit much and some of the connectors are a pain to get to if they were supposed to be diagnostic. Attached are some pics so you can get an idea of what i am talking about, one comes off of main harness on firewall and goes nowhere, and about halfway down harness it has a little bracket like the harness should be connected somewhere. Another one is just to the left of battery box, one is underneath/behind the middle of battery box and the last one is behind middle of batter tray and looks like harness leads to a bigger harness that goes to power distribution center. And I have searched and can't find anything these connectors are supposed to connect to, here are pics for clarification.