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So I'm sorting through all the crap the previous owner/s did to this truck. As can seen in the picture, there's a toggle switch mounted to the side of the trailer brake. It runs into the engine bay, down the harness on the frame rail, on top of the transmission where it disappears.
<a href='http://postimg.org/image/guga90wnz/full/' target='_blank'><img src='http://s19.postimg.org/4fti8p55v/20160420_100500.jpg' border='0' alt="20160420 100500" /></a><br />
Besides a possible torque converter lock-up switch, what other switches would somebody wire to the transmission?
Who knows. It could be anything - reverse light switch, fake neutral switch, etc.. Turn it on and see what happens.
Looks to be a Torque Converter Lockup switch. When it is engaged, the computer throws a P0743 code and the OD light blinks. When its disengaged, code goes away and everything is good.
I was worried that the transmission would be toast. Took off the torque converter access plug, and it's as clean as can be under there, the PO did say it was rebuilt within the last 10K but I thought he was full of it because he didn't have paper work on it