Counter Gear Speed Sensor
WARNING: This page is about a different car, the 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
Counter gear speed sensor (NC) detects rotation of counter drive gear. By comparing counter gear speed sensor signal and input turbine speed sensor (NT) signal, ECM detects shift timing of gears and controls engine torque and hydraulic pressure in response to various conditions, resulting in smooth transaxle shifting. See Fig 1.