Infiniti Q45. Manual - part 29

A/T CONTROL SYSTEM

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TCM Function

NCS000TT

The function of the TCM is to:

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Receive input signals sent from various switches and sensors.

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Determine required line pressure, shifting point, lock-up operation, and engine brake operation.

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Send required output signals to the respective solenoids.

CONTROL SYSTEM OUTLINE 

The A/T senses vehicle operating conditions through various sensors or signals. It always controls the opti-
mum shift position and reduces shifting and lock-up shocks.

CONTROL SYSTEM DIAGRAM

SENSORS (or SIGNAL)

Þ

TCM

Þ

ACTUATORS

PNP switch
Accelerator pedal position signal
Closed throttle position signal
Wide open throttle position signal
Engine speed signal
A/T fluid temperature sensor
Revolution sensor
Vehicle speed signal
Manual mode switch signal
Stop lamp switch signal
Turbine revolution sensor
ATF pressure switch

Shift control
Line pressure control
Lock-up control
Engine brake control
Timing control
Fail-safe control
Self-diagnosis
CONSULT-II communication line
Duet-EA control
CAN system

Input clutch solenoid valve 
Direct clutch solenoid valve 
Front brake solenoid valve
High and low reverse clutch 
solenoid valve
Low coast brake solenoid valve
Torque converter clutch solenoid 
valve
Line pressure solenoid valve
A/T CHECK indicator lamp
Back-up lamp relay
Park/neutral position relay

SCIA5861E

AT-30

A/T CONTROL SYSTEM

CAN Communication

NCS000TU

SYSTEM DESCRIPTION 

CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle mul-
tiplex communication line with high data communication speed and excellent error detection ability. Many elec-
tronic control units are equipped onto a vehicle, and each control unit shares information and links with other
control units during operation (not independent). In CAN communication, control units are connected with 2
communication lines (CAN-H line, CAN-L line) allowing a high rate of information transmission with less wiring.
Each control unit transmits/receives data but selectively reads required data only. Refer to 

LAN-40, "CAN

Communication Unit"

 .

Input/Output Signal of TCM

NCS000TV

*1: Spare for vehicle speed sensor·A/T (revolution 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: Used as a condition for starting self-diagnostics; if self-diagnostics are not started, it is judged that there is some kind of error.
*5: Input by CAN communications.
*6: Output by CAN communications.

Control item

Line

pressure

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 

(*5)

X

X

X

X

X

X

X

Vehicle speed sensor A/T
(revolution sensor)

X

X

X

X

X

X

X

Vehicle speed sensor MTR

(*1) (*5)

X

Closed throttle position signal

(*5)

X (*2)

X

X

X

X (*4)

Wide open throttle position signal

(*5)

X

X  (*4)

Turbine revolution sensor 1

X

X

X

X

X

Turbine revolution sensor 2
(for 4th speed only)

X

X

X

X

X

Engine speed signals

(*5)

X

X

X

X

X

X

X

Stop lamp switch signal

(*5)

X

X

X

X  (*4)

A/T  fluid  temperature  sensors  1,  2

X

X

X

X

X

X

ASCD or ICC

Operation signal

(*5)

X

X

X

Overdrive cancel 

signal

(*5)

X

Out-
put

Direct clutch solenoid (ATF pressure 
switch 5)

X

X

X

X

Input clutch solenoid (ATF pressure 
switch 3)

X

X

X

X

High and low reverse clutch solenoid 
(ATF pressure switch 6)

X

X

X

X

Front brake solenoid (ATF pressure 
switch 1)

X

X

X

X

Low coast brake solenoid (ATF pres-
sure switch 2)

X

X

X

X

X

Line pressure solenoid

X

X

X

X

X

X

X

TCC solenoid

X

X

X

Self-diagnostics table

(*6)

X

Park/neutral position relay

X

X

A/T CONTROL SYSTEM

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Line Pressure Control

NCS000TW

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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.

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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.

LINE PRESSURE CONTROL IS BASED ON THE TCM LINE PRESSURE CHARACTERISTIC 
PATTERN 

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The TCM has stored in memory a number of patterns for the optimum line pressure characteristic for the
driving state.

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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.

PCIA0007E

PCIA0008E

PCIA0009E

AT-32

A/T CONTROL SYSTEM

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 is
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

NCS000TX

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.

PCIA0010E

PCIA0011E

PCIA0012E