DTC P0734 A/T 4TH Gear Function: Description: Notes

WARNING: This page is about a different car, the 2004 Nissan Maxima. However, it is still accessible from the selected car via links, so may be relevant.

This malfunction will not be detected while the A/T CHECK indicator lamp is indicating another self-diagnosis malfunction.
This malfunction is detected when the A/T does not shift into fourth gear position or the torque converter clutch does not lock up as instructed by the TCM. This is not caused by electrical malfunction (circuits open or shorted) but by mechanical malfunction such as control valve sticking, improper solenoid valve operation, malfunctioning oil pump or torque converter clutch, etc.

Fig 1: Shift Solenoid Valve Operation Table
Courtesy of NISSAN MOTOR CO., U.S.A.