Nissan Pathfinder (2006 year). Manual - part 5

A/T CONTROL SYSTEM

AT-31

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2006 Pathfinder

“R” Position

●

The front brake fastens the front sun gear.

●

The high and low reverse clutch is coupled, and the mid sun gear and rear sun gear are connected.

●

The reverse brake fastens the rear carrier.

1.

Front brake

2.

Input clutch

3.

Direct clutch

4.

High and low reverse clutch

5.

Reverse brake

6.

Forward brake

7.

Low coast brake

8.

1st one-way clutch

9.

Forward one-way clutch

10. 3rd one-way clutch

11.

Front sun gear

12. Input shaft

13. Mid internal gear

14. Front internal gear

15. Rear carrier

16. Rear sun gear

17. Mid sun gear

18. Front carrier

19. Mid carrier

20. Rear internal gear

21. Output shaft

22. Parking gear

23. Parking pawl

SCIA1519E

AT-32

A/T CONTROL SYSTEM

2006 Pathfinder

TCM Function

ECS00EEO

The function of the TCM is to:

●

Receive input signals sent from various switches and sensors.

●

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

●

Send required output signals to the respective solenoids.

CONTROL SYSTEM OUTLINE 

The automatic transmission senses vehicle operating conditions through various sensors or signals. It always
controls the optimum shift position and reduces shifting and lock-up shocks.

CONTROL SYSTEM DIAGRAM 

SENSORS (or SIGNALS)

Þ

TCM

Þ

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-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
O/D OFF indicator lamp
Starter relay
Back-up lamp relay

SCIA6495E

A/T CONTROL SYSTEM

AT-33

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2006 Pathfinder

CAN Communication

ECS00EEP

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-30,

"CAN Communication Unit"

 .

Input/Output Signal of TCM

ECS00EEQ

*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: 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 

(*4)

X

X

X

X

X

X

X

Vehicle speed sensor A/T
(revolution sensor)

X

X

X

X

X

X

Vehicle speed sensor MTR

(*1) (*4)

X

X

X

X

X

Closed throttle position signal

(*4)

X(*2)

X(*2)

X

X(*2)

X

Wide open throttle position signal

(*4)

X(*2)

X(*2)

X(*2)

X

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

(*4)

X

X

PNP  switch

X

X

X

X

X

X

X

Stop lamp switch signal

(*4)

X

X

X

A/T  fluid  temperature  sensors  1,  2

X

X

X

X

X

X

X

ASCD

Operation signal

(*4)

X

X

X

X

Overdrive cancel 

signal

(*4)

X

X

X

TCM power supply voltage signal

X

X

X

X

X

X

Out-
put

Direct clutch solenoid (ATF pres-
sure 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

Starter relay

X

X

AT-34

A/T CONTROL SYSTEM

2006 Pathfinder

Line Pressure Control

ECS00EER

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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.

●

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 

●

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.

PCIA0007E

PCIA0008E

PCIA0009E

A/T CONTROL SYSTEM

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2006 Pathfinder

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
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

ECS00EES

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.

PCIA0010E

PCIA0011E

PCIA0012E

AT-36

A/T CONTROL SYSTEM

2006 Pathfinder

Shift Change System Diagram

*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

ECS00EET

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.

PCIA0013E

Select lever

D position

3 position

2 position

Gear  position

5

4

3

2

Lock-up

×

–

×

×

Slip lock-up

×

×

–

–

PCIA0014E

A/T CONTROL SYSTEM

AT-37

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2006 Pathfinder

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 cou-
pling 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

ECS00EEU

●

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.

SCIA1520E

AT-38

A/T CONTROL SYSTEM

2006 Pathfinder

Control Valve

ECS00EEV

FUNCTION OF CONTROL VALVE 

FUNCTION OF PRESSURE SWITCH 

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.

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 
(input 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 
(direct clutch pressure) and supplies it to the direct clutch. (In 2nd, 3rd, and 4th gears, 
adjusts 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

Pressure switch 1 (FR/B)

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

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.

Pressure switch 3 (I/C)

Detects any malfunction in the input clutch hydraulic pressure. When it detects any mal-
function, it puts the system into fail-safe mode.