I had the fast idle on an upfitter switch in my 2008, and today tried setting it up on the 2019. Wired upfitter switch 4, over to the passthrough wires, wired that to the yellow/green wire. Added 20k ohm resister between the green and the white/brown. Confirmed I am getting power to the wire when i turn on the switch. Confirmed I have 20k ohms between those two wires. Set parking brake, turn on switch,,,,, no change in rpm? Is there something else I am overlooking? I have made some changes in forscan for other things, but don't know of anything that would change this, and even looked through it again and can't find anything related. What am I missing?

 

Are you sure you are on the correct yellow/green wire ? There are two - one for the diesel trucks, one for the gas trucks. This is the connector in the passenger footwell.

I made this diagram some time back - hope it helps.

 

What he said^^^

With the diesel you want the yellow with green that is pinned (pin 7) on the same row as the other two wires (pin 9 and 10) you used for the resistor.

 

Hmmm,,,,, I didn't realize there are two. I'll go confirm, and hope it's really that simple. Thank you!

Edit: That was it!!! Why would they put two wires of the same color right next to each other in a bundle? I've seen stranger things. Thanks again!