mystery wiring harness.

[toyplumbertrucks]

I am starting to part out a Jimmy I picked up, I bought it for the frame and transmission. Anyway while I was removing all the wiring that looked factory I came across this relay harness that went through the firewall by itself. It was loose in the engine compartment so I am not sure what it is for.it has a thick red wire and 3 smaller wires (brown/white, blue, black/white, on the inside.On the engine side there is a red plug, a single black plug, and the blue wire and brown/white wire go to another plug where there is a green/white wire connected to the blue wire. Anybody know what it is for? I don't have this think on my other blazer or k2o.