It's located on the firewall right behind the intake manifold, any idea what this is used for? Should it be plugged into something?

 

there should be a bolt that has a ground wire coming off it, that should clip into that, its a rear grounding wire.

 

A ground for what? I'm just trying to understand more about my truck. For as long as I have owned it, it has never been connected to anything. Are there any sort of negative impacts of this not being grounded to the firewall?

 

Any ideas?

 

The wiring diagram:
http://www.ncttora.com/fsm/1990-1995...5/contents.htm

 

According to the diagram that is the main ground for my transmission and ecu, which would explaIn why my tranny won't shift automatically and why I'm getting a short CIRCUT code for every solenoid for my transmission... Upon further investigation I am unable to locate the other end of that wire that comes from the main harness. Any idea where the harness side of that wire is located?

 

Take a look at the 6th and 7th engine bay pics...it looks like the plug on the center of the firewall connecting to the ground?
https://www.yotatech.com/forums/f116...ebuild-244314/

 

There's another plug that bolts onto the top of the intake.... then you plug em together. Toyotas and any vehicle for that matter love thier grounds more so with computer controlled vehicles. If it says it needs to be there you should put it there. You could even make your own, it's only about 6" long and a couple of crimp fittings, it's not electrical it just plugs together.

I had a 94 pickup that would start bucking for no reason but only when it was on the freeway and not all the time. It turned out to be a faulty ground for something, I fixed it and never had the problem again.