LOCK-UP AND SELECT CONTROL SYSTEM: System Description

• 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 conventional A/T models.
• If the CVT fluid temperature is low or the vehicle is in fail-safe mode due to malfunction, lock-up control is prohibited.
  Fig 1: Identifying Throttle Opening Vs Vehicle Speed Graph

  Courtesy of NISSAN NORTH AMERICA, INC.

Lock-up Released

In the lock-up released state, the torque converter clutch control valve is set into the unlocked state by the torque converter clutch solenoid valve and the lock-up apply pressure is drained.

In this way, the torque converter clutch piston is not coupled.

Lock-up Applied

In the lock-up applied state, the torque converter clutch control valve is set into the locked state by the torque converter clutch solenoid valve and lock-up apply pressure is generated.

In this way, the torque converter clutch piston is pressed and coupled.

Select Control

When shifting between "N" ("P") ==> "D" ("R"), optimize the operating pressure on the basis of the throttle position, the engine speed, and the secondary pulley (output) revolution speed to lessen the shift shock.