System Description: Notes

The torque converter clutch piston in the torque converter is engaged to eliminate torque converter slip to increase power transmission efficiency.
The torque converter clutch control valve operation is controlled by the torque converter clutch solenoid valve, which is controlled by a signal from TCM. The torque converter clutch control valve engages or releases the torque converter clutch piston.
When shifting between "N" ("P") ==> "D" ("R"), torque converter clutch solenoid valve controls engagement power of forward clutch and reverse brake.
The lock-up applied gear range was expanded by locking up the torque converter at a lower vehicle speed than AT models.
Lock-up is prohibited when CVT fluid temperature is low.

Fig 1: Identifying CVT Lock-Up Area Graph
Courtesy of NISSAN NORTH AMERICA, INC.