Circuit/System Description

WARNING: This page is about a different car, the 2017 GMC Acadia. However, it is still accessible from the selected car via links, so may be relevant.

When the shift lever is placed in the M position, electronic range select or manual mode, which allows for the selection of the range of gears available, is activated. Manual mode allows the vehicle operator to increase the highest transmission gear available by pressing the plus (+) button or decrease the highest gear available by pressing the minus (-) button. The body control module (BCM) supplies a signal circuit to the shift controller. The shift controller has switches connected to a resistor array. A voltage drop occurs across the resistor network. When the plus or minus button is pushed, a corresponding voltage drop occurs across the resistor network. This voltage drop is monitored by the BCM. The BCM will send the request to the transmission control module (TCM) to increase or decrease the available gear. The TCM will not allow a downshift if the engine would be compromised by overspeeding.