Transmission Control Switch Circuit: Description
WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.
The transmission control switch detects when the shift lever is moved to M.
Using the transmission control switch, when the shift lever is in M, it is possible to select between 1st and 8th gears (M1 to M8).
Moving the shift lever to "+" once selects the next higher gear, and moving the shift lever to "-" once selects the next lower gear.