There are two different types of speed sensors in the 2015 Nissan Altima. One is the transmission speed sensor. This is located on the tail shaft of the transmission and monitors the speed of the transmission shaft. The center sends a signal to the computer depending on the speed of the shaft and well either shift the gears up or down. The other type of speed sensor is a wheel speed sensor</br> this is part of the abse system. This sensor's job is to monitor the speed of the wheel the computer looks at all the information from each of the wheels and if it notices that one of the wheels are spinning faster or slower than the others it will adjust the speed to stop the wheel from losing traction.