LOCK-UP CONTROL: System Description: Notes

• The torque converter clutch piston in the torque converter is engaged to eliminate torque converter slip to increase power transmission efficiency.
• Lock-up operation, however, is prohibited when A/T fluid temperature is too low.
• The torque converter clutch control valve operation is controlled by the torque converter clutch solenoid valve, which is controlled by a signal from TCM, and the torque converter clutch control valve engages or releases the torque converter clutch piston.
  Fig 1: Lock-Up Control Operation Diagram

  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 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 and lock-up apply pressure is generated.

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