Transmission Manual Shift Switch - Up/Down
WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.
The transmission manual shift switch is mounted on the transmission gear shift lever handle. The manual shift switch is a momentary type that has three positions. The three positions are neutral or open, plus (+) for upshifts and minus (-) for downshifts. When selecting a gear, a number 1 through 6 for 6L transmission and 1 through 8 for 8L transmissions, will be displayed next to the letter M on the instrument panel, to indicate the current gear the operator has selected.
The transmission manual shift switch is an input signal to the body control module. The upshift or downshift signal commands are processed and sent out on the serial data line from the body control module to the engine control module and transmission control module.