Nissan Titan. Manual - part 586

A/T CONTROL SYSTEM

TM-27

< SYSTEM DESCRIPTION >

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• This line pressure solenoid controls the pressure regulator valve as the signal pressure and adjusts the pres-

sure of the operating oil discharged from the oil pump to the line pressure most appropriate to the driving

state.

LINE PRESSURE CONTROL IS BASED ON THE TCM LINE PRESSURE CHARACTERISTIC PAT-
TERN 

• 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.

Back-up Control (Engine Brake)

When the select operation is performed during driving and the trans-

mission is shifted down, the line pressure is set according to the

vehicle speed.

During Shift Change

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PCIA0008E

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TM-28

< SYSTEM DESCRIPTION >

A/T CONTROL SYSTEM

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 is

set according to engine speed, during engine brake operation.

At Low Fluid Temperature

When the A/T fluid temperature drops below the prescribed tempera-

ture, in order to speed up the action of each friction element, the line

pressure is set higher than the normal line pressure characteristic.

Shift Control

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The clutch pressure control solenoid is controlled by the signals from the switches and sensors. Thus, the

clutch pressure is adjusted to be appropriate to the engine load state and vehicle driving state. It becomes

possible to finely control the clutch hydraulic pressure with high precision and a smoother shift change charac-

teristic is attained.

SHIFT CHANGE 

The clutch is controlled with the optimum timing and oil pressure by the engine speed, engine torque informa-

tion, etc.

Shift Change System Diagram

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PCIA0012E

A/T CONTROL SYSTEM

TM-29

< SYSTEM DESCRIPTION >

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*1: Full phase real-time feedback control monitors movement of gear ratio at gear change, and controls oil

pressure at real-time to achieve the best gear ratio.

Lock-up Control

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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, and the torque converter clutch control valve engages or releases

the torque converter clutch piston.

Lock-up Operation Condition Table (Floor Shift Models)

Lock-up Operation Condition Table (Column Shift Models)

TORQUE CONVERTER CLUTCH CONTROL VALVE CONTROL 

Lock-up Control System Diagram

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.

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Select lever

D position

4 position

3 position

2 position

Gear  position

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Lock-up

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Slip lock-up

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Select lever

D position

M position

Gear  position

5

4

3

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Lock-up

×

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Slip lock-up

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PCIA0014E

TM-30

< SYSTEM DESCRIPTION >

A/T CONTROL SYSTEM

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.

SMOOTH LOCK-UP CONTROL 

When shifting from the lock-up released state to the lock-up applied state, the current output to the torque con-

verter clutch solenoid is controlled with the TCM. In this way, when shifting to the lock-up applied state, the

torque converter clutch is temporarily set to the half-clutched state to reduce the shock.

Half-clutched State

• The current output from the TCM to the torque converter clutch solenoid is varied to gradually increase the

torque converter clutch solenoid pressure.

In this way, the lock-up apply pressure gradually rises and while the torque converter clutch piston is put into

half-clutched status, the torque converter clutch piston operating pressure is increased and the coupling is

completed smoothly.

Slip Lock-up Control

• In the slip region, the torque converter clutch solenoid current is controlled with the TCM to put it into the

half-clutched state. This absorbs the engine torque fluctuation and lock-up operates from low speed.

This raises the fuel efficiency for 4GR and 5GR at both low speed and when the accelerator has a low

degree of opening.

Engine Brake Control

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• The forward one-way clutch transmits the drive force from the engine to the rear wheels. But the reverse

drive from the rear wheels is not transmitted to the engine because the one-way clutch is idling.

Therefore, the low coast brake solenoid is operated to prevent the forward one-way clutch from idling and

the engine brake is operated in the same manner as conventionally.

• The operation of the low coast brake solenoid switches the low coast brake switching valve and controls the

coupling and releasing of the low coast brake.

The low coast brake reducing valve controls the low coast brake coupling force.

Control Valve

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FUNCTION OF CONTROL VALVE 

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Name

Function

Torque converter regulator valve

In order to prevent the pressure supplied to the torque converter from being excessive, 
the line pressure is adjusted to the optimum pressure (torque converter operating pres-
sure).

Pressure regulator valve
Pressure regulator plug
Pressure regulator sleeve

Adjusts the oil discharged from the oil pump to the optimum pressure (line pressure) for 
the driving state.