WHICH wire to ground?

[dieselgirlanddan]

I want to bypass the pcm completly and put overdrive on a manual toggle switch. I know that there's a wire you ground to do this, my question is WHICH particular wire at the transmission do I ground?

 

[cerberusiam]

It is the smaller of the two that are in the plug on the trans. Off the top of my head it is the black wire with orange stripe. If you pull the plug and use a tester it will be the one with no power on it.