Nissan Pathfinder (2008 year). Manual - part 585

TM-22

< FUNCTION DIAGNOSIS >

A/T CONTROL SYSTEM

CONTROL SYSTEM DIAGRAM 

CONTROL SYSTEM OUTLINE (WITH MANUAL MODE)

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.

SENSORS (or SIGNALS)

⇒

TCM

⇒

ACTUATORS

PNP switch
Accelerator pedal position sensor
Closed throttle position signal
Wide open throttle position signal
Engine speed signal
A/T fluid temperature sensor
Revolution sensor
Vehicle speed signal
Stop lamp switch signal
Turbine revolution sensor
1st position switch signal
Overdrive control switch signal
ATF pressure switch signal

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

Input clutch solenoid valve 
Direct clutch solenoid valve 
Front brake solenoid valve
High and low reverse clutch sole-
noid valve
Low coast brake solenoid valve
Torque converter clutch solenoid 
valve
Line pressure solenoid valve
O/D OFF indicator lamp
Starter relay
Back-up lamp relay

AWDIA0073GB

SENSORS (or SIGNALS)

⇒

TCM

⇒

ACTUATORS

PNP switch
Accelerator pedal position sensor
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 signal

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

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

A/T CONTROL SYSTEM

TM-23

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CONTROL SYSTEM DIAGRAM 

CAN Communication

INFOID:0000000001282731

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. For details, refer to 

LAN-56,

"CAN System Specification Chart"

.

AWDIA0074GB

TM-24

< FUNCTION DIAGNOSIS >

A/T CONTROL SYSTEM

Input/Output Signal of TCM

INFOID:0000000001282732

*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-diagnosis; if self-diagnosis are not started, it is judged that there is some kind of error

*5: Input by CAN communications

*6: Output by CAN communications

Line Pressure Control

INFOID:0000000001282733

• 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

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

Operation signal

(*4)

X

X

X

Overdrive cancel sig-

nal

(*5)

X

Output

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 sole-
noid 
(ATF pressure switch 6)

X

X

X

X

Front brake solenoid 
(ATF pressure switch 1)

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

Self-diagnosis table

(*6)

X

Starter relay

X

X

A/T CONTROL SYSTEM

TM-25

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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

PCIA0007E

PCIA0008E

PCIA0009E

TM-26

< 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:0000000001282734

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-27

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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

INFOID:0000000001282735

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

3 position

2 position

Gear position

5

4

3

2

Lock-up

×

–

–

–

Slip lock-up

×

×

–

–

PCIA0014E

TM-28

< FUNCTION DIAGNOSIS >

A/T CONTROL SYSTEM

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 4th and 5th gears at both low speed and when the accelerator has a low
degree of opening.

Engine Brake Control

INFOID:0000000001282736

• 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

INFOID:0000000001282737

FUNCTION OF CONTROL VALVE 

SCIA1520E

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.

Front brake control valve

When the front brake is coupled, adjusts the line pressure to the optimum pressure (front 
brake pressure) and supplies it to the front brake. (In 1st, 2nd, 3rd, and 5th gears, adjusts 
the clutch pressure.)

Accumulator control valve

Adjusts the pressure (accumulator control pressure) acting on the accumulator piston 
and low coast reducing valve to the pressure appropriate to the driving state.

A/T CONTROL SYSTEM

TM-29

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FUNCTION OF PRESSURE SWITCH 

Pilot valve A

Adjusts the line pressure and produces the constant pressure (pilot pressure) required 
for line pressure control, shift change control, and lock-up control.

Pilot valve B

Adjusts the line pressure and produces the constant pressure (pilot pressure) required 
for shift change control.

Low coast brake switching valve

During engine braking, supplies the line pressure to the low coast brake reducing valve.

Low coast brake reducing valve

When the low coast brake is coupled, adjusts the line pressure to the optimum pressure 
(low coast brake pressure) and supplies it to the low coast brake.

N-R accumulator

Produces the stabilizing pressure for when N-R is selected.

Direct clutch piston switching valve

Operates in 4th gear and switches the direct clutch coupling capacity.

High and low reverse clutch control valve

When the high and low reverse clutch is coupled, adjusts the line pressure to the opti-
mum pressure (high and low reverse clutch pressure) and supplies it to the high and low 
reverse clutch. (In 1st, 3rd, 4th and 5th gears, adjusts the clutch pressure.)

Input clutch control valve

When the input clutch is coupled, adjusts the line pressure to the optimum pressure (in-
put clutch pressure) and supplies it to the input clutch. (In 4th and 5th gears, adjusts the 
clutch pressure.)

Direct clutch control valve

When the direct clutch is coupled, adjusts the line pressure to the optimum pressure (di-
rect clutch pressure) and supplies it to the direct clutch. (In 2nd, 3rd, and 4th gears, ad-
justs the clutch pressure.)

TCC control valve
TCC control plug
TCC control sleeve

Switches the lock-up to operating or released. Also, by performing the lock-up operation 
transiently, lock-up smoothly.

Torque converter lubrication valve

Operates during lock-up to switch the torque converter, cooling, and lubrication system 
oil path.

Cool bypass valve

Allows excess oil to bypass cooler circuit without being fed into it.

Line pressure relief valve

Discharges excess oil from line pressure circuit.

N-D accumulator

Produces the stabilizing pressure for when N-D is selected.

Manual valve

Sends line pressure to each circuit according to the select position. The circuits to which 
the line pressure is not sent drain.

Name

Function

Name

Function

Pressure switch 2 (LC/B)

Detects any malfunction in the low coast brake hydraulic pressure. When it detects any 
malfunction, it puts the system into fail-safe mode.