At vehicle speeds of 12 mph (20 km/h) or more, the PCM, which monitors the signals from the output shaft (countershaft) speed sensor, activates the reverse lockout solenoid, which pushes select lock cam into the select lock pin. As a result, the select lever cannot rotate to the reverse select position, making it impossible to engage reverse gear. As the vehicle speed drops to 9 mph (15 km/h) or less, the PCM turns off the reverse lockout solenoid. The select lock return spring pulls back select lock cam, enabling the select lever to move freely so reverse gear can be selected.