That is the Acceleration Slip Regulation; It works with your Anti lock Brake/Traction Control system. The ASR monitors the Steering angle sensor & Accelerator position sensor. Wheel speed is continuously monitored by the ASR module. It controls the braking of the rear wheels when it has noticed a slipping of the wheels until the slip has been corrected. It does not plug into the transmission. It is used to turn off the traction control.