Circuit/System Description

When the shift lever is placed left of the D position, the driver shift request (DSR), also known as the tap shift function, is activated. The DSR allows the vehicle operator to shift gears by pushing the shift lever forward for an upshift or pulling the shift lever rearward for a downshift. The BCM supplies battery voltage, ground and a signal circuit to the shift controller. The shift controller has Hall-effect switches connected to a resistor array. When the lever is left of the position, then pushed forward for an upshift, or pulled rearward for a downshift, 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 to perform the upshift or downshift. The TCM is constantly monitoring the serial data sent from the BCM for the correct number and sequence of counts for Tap Up and Tap Down function.