[projectRDM]

There's a switch on the side of the transmission, it signals the ATC based on gear position. The starter signal wire is tied into the switch and only makes contact when in N or P. The switch is adjustable a bit, as in you can loosen the bolts securing it and rotate it to better align the gear selections, I've seen switches wear and begin to engage D in the 2 position and such, and the switch does wear out completely, I've replaced one before and sold a few as well. You can remove it and check continuity right at the base.