Some help identifying a plug
 

I was under the truck today trying to track down a small leak (insert joke here) and noticed two plugs hanging down. They are near the transmission fluid pan (top of pic). Two small plugs, about mid pic a bit to leftaxbove heat shield. You could see black one in pic. Truck is 04 HSE with air suspension and no ACE. Looked in Rave but didn't help me.
Attachment 39707

Not sure but my guess is it's used for ACE.

That is what I was thinking. My 00 had ACE and I don't remember wires though there (and I had to do trans cooler lines so I was all up in there too). Of course, I just finally sold that one last week so I can't look. Always great timing lol

I've been wondering what those go to for a while. Neither one of mine have those hooked to anything.

I think it's an additional temp sensor that was only on certain year cars.