Infiniti QX56 (JA60). Manual - part 930

TM-22

< FUNCTION DIAGNOSIS >

A/T CONTROL SYSTEM

Input/Output Signal of TCM

INFOID:0000000005148512

*1: Spare for output speed sensor
*2: Spare for accelerator pedal position signal
*3: If these input and output signals are different, the TCM triggers the fail-safe function.
*4: CAN communications
*5: Used as a condition for starting self-diagnostics; if self-diagnostics are not started, it is judged that there is some kind of error.
*6: A/T fluid temperature sensor 2 does not have any function.

Line Pressure Control

INFOID:0000000005148513

• When an input torque signal equivalent to the engine drive force is sent from the ECM to the TCM, the TCM

controls the line pressure solenoid.

Control item

Line

pres-

sure

control

Vehicle 

speed 

control

Shift     

control

Lock-up 

control

Engine 

brake 

control

Fail-safe 

function 

(*3)

Self-diag-

nostics 

function

Input

Accelerator pedal position signal 

(*4)

X

X

X

X

X

X

X

Output speed sensor

X

X

X

X

X

X

Vehicle speed signal

(*1) (*4)

X

X

X

X

X

Closed throttle position signal

(*4)

(*2) X

(*2) X

X

(*2) X

(*5) X

Wide open throttle position signal

(*4)

(*2) X

(*2) X

(*2) X

(*5) X

Input speed sensor 1

X

X

X

X

X

Input speed sensor 2
(for 4th speed only)

X

X

X

X

X

Engine speed signals

(*4)

X

X

Transmission range switch

X

X

X

X

X

X

X

Stop lamp switch signal

(*4)

X

X

X

(*5)  X

A/T fluid temperature sensors 1, 2 (*6)

X

X

X

X

X

X

X

ASCD

Operation signal

(*4)

X

X

X

X

Overdrive cancel sig-
nal

(*4)

X

X

X

TCM power supply voltage signal

X

X

X

X

X

X

Output

Direct clutch solenoid

X

X

X

X

Input clutch solenoid

X

X

X

X

High and low reverse clutch solenoid

X

X

X

X

Front brake solenoid

X

X

X

X

Low coast brake solenoid (ATF pressure 
switch 2)

X

X

X

X

X

Line pressure solenoid

X

X

X

X

X

X

X

TCC solenoid

X

X

X

Starter relay

X

X

A/T CONTROL SYSTEM

TM-23

< FUNCTION DIAGNOSIS >

C

E

F

G

H

I

J

K

L

M

A

B

TM

N

O

P

• 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

PCIA0007E

PCIA0008E

PCIA0009E

TM-24

< FUNCTION DIAGNOSIS >

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

INFOID:0000000005148514

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

PCIA0010E

PCIA0011E

PCIA0012E

A/T CONTROL SYSTEM

TM-25

< FUNCTION DIAGNOSIS >

C

E

F

G

H

I

J

K

L

M

A

B

TM

N

O

P

*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

INFOID:0000000005148515

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

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.

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 

PCIA0013E

Select lever

D position

4 position

3 position

2 position

Gear  position

5

4

4

3

2

Lock-up

×

–

×

×

×

Slip lock-up

×

×

–

–

–

PCIA0014E