Line Pressure Control

• When an input torque signal equivalent to the engine drive force is transmitted from the ECM to the TCM, the TCM controls the line pressure solenoid valve.
• This line pressure solenoid controls the pressure regulator valve as the signal pressure and adjusts the pressure of the operating oil discharged from the oil pump to the line pressure most appropriate to the driving state.
  Fig 1: Line Pressure Control Diagram

  Courtesy of NISSAN NORTH AMERICA, INC.

Line Pressure Control is Based On The TCM Line Pressure Characteristic Pattern

• The TCM has stored in memory a number of patterns for the optimum line pressure characteristic for the driving state.
• In order to obtain the most appropriate line pressure characteristic to meet the current driving state, the TCM controls the line pressure solenoid current value and thus controls the line pressure.

Normal Control

• Each clutch is adjusted to the necessary pressure to match the engine drive force.
  Fig 2: TCM Line Pressure Characteristic Pattern - Normal Control

  Courtesy of NISSAN NORTH AMERICA, INC.

Back-up Control (Engine Brake)

• When the select operation is performed during driving and the A/T is shifted down, the line pressure is set according to the vehicle speed.
  Fig 3: TCM Line Pressure Characteristic Pattern - Back-Up Control (Engine Brake)

  Courtesy of NISSAN NORTH AMERICA, INC.

During Shift Change

• The necessary and adequate line pressure for shift change is set. For this reason, line pressure pattern setting corresponds to input torque and gearshift selection. Also, line pressure characteristic corresponds to engine speed, during engine brake operation.
  Fig 4: TCM Line Pressure Characteristic Pattern - During Shift Change

  Courtesy of NISSAN NORTH AMERICA, INC.

At Low Fluid Temperature

• When the A/T fluid temperature drops below the prescribed temperature, in order to speed up the action of each friction element, the line pressure is set higher than the normal line pressure characteristic.
  Fig 5: TCM Line Pressure Characteristic Pattern - At Low Fluid Temperature

  Courtesy of NISSAN NORTH AMERICA, INC.