Conditions for Lock-up Operation
WARNING: This page is about a different car, the 2003 Infiniti I35. However, it is still accessible from the selected car via links, so may be relevant.
When vehicle is driven in 3rd or 4th gear positions, vehicle speed and throttle opening are detected. If the detected values fall within the lock-up zone memorized in the TCM, lock-up is performed.
Courtesy of NISSAN MOTOR CO., U.S.A.