Nissan Frontier D22. Manual - part 52

OVERALL SYSTEM

AT-177

[RE4R01A]

D

E

F

G

H

I

J

K

L

M

A

B

AT

Control System

ECS007LK

OUTLINE

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

CONTROL SYSTEM

SENSORS

TCM

ACTUATORS

PNP switch
Throttle position sensor
Closed throttle position switch
Wide open throttle position switch
Engine speed signal
A/T fluid temperature sensor
Revolution sensor
Vehicle speed sensor
Overdrive control switch
ASCD control unit
Stop lamp switch (VG33ER only)
Turbine revolution sensor 
(VG33ER only)

Shift control
Line pressure control
Lock-up control
Overrun clutch control
Timing control
Fail-safe control
Self-diagnosis
CONSULT-II communication line
Duet-EA control

Shift solenoid valve A
Shift solenoid valve B
Overrun clutch solenoid valve
Torque converter clutch solenoid 
valve
Line pressure solenoid valve
O/D OFF indicator lamp

WAT495

AT-178

[RE4R01A]

OVERALL SYSTEM

TCM FUNCTION

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.

INPUT/OUTPUT SIGNAL OF TCM

Control Mechanism

ECS007LL

LINE PRESSURE CONTROL

TCM has the various line pressure control characteristics to meet the driving conditions.
An ON-OFF duty signal is sent to the line pressure solenoid valve based on TCM characteristics.
Hydraulic pressure on the clutch and brake is electronically controlled through the line pressure solenoid valve
to accommodate engine torque. This results in smooth shift operation.

Normal Control

The line pressure to throttle opening characteristics is set for suitable
clutch operation.

Sensors and solenoid valves

Function

Input

PNP switch

Detects select lever position and sends a signal to TCM.

Throttle position sensor

Detects throttle valve position and sends a signal to TCM.

Closed throttle position switch

Detects throttle valve's fully-closed position and sends a signal to TCM.

Wide open throttle position switch

Detects a throttle valve position of greater than 1/2 of full throttle and sends a 
signal to TCM.

Engine speed signal

From ECM.

A/T fluid temperature sensor

Detects transmission fluid temperature and sends a signal to TCM.

Revolution sensor

Detects output shaft rpm and sends a signal to TCM.

Vehicle speed sensor

Used as an auxiliary vehicle speed sensor. Sends a signal when revolution 
sensor (installed on transmission) malfunctions.

Overdrive control switch

Sends a signal, which prohibits a shift to D

4

  (overdrive) position, to the TCM.

ASCD control unit

Sends the cruise signal and D

4

  (overdrive) cancellation signal from ASCD 

control unit to TCM.

Turbine revolution sensor (VG33ER 
only)

Sends the input shaft revolution signal.

Stop lamp switch (VG33ER only)

Sends the lock-up release signal to the TCM at the time of D

4

  (lock-up)

Output

Shift solenoid valve A/B

Selects shifting point suited to driving conditions in relation to a signal sent 
from TCM.

Line pressure solenoid valve

Regulates (or decreases) line pressure suited to driving conditions in relation 
to a signal sent from TCM.

Torque converter clutch solenoid 
valve

Regulates (or decreases) lock-up pressure suited to driving conditions in rela-
tion to a signal sent from TCM.

Overrun clutch solenoid valve

Controls an “engine brake” effect suited to driving conditions in relation to a 
signal sent from TCM.

O/D OFF indicator lamp

Shows TCM faults, when A/T control components malfunction.

SAT003J

OVERALL SYSTEM

AT-179

[RE4R01A]

D

E

F

G

H

I

J

K

L

M

A

B

AT

Back-up Control (Engine brake)

If the selector lever is shifted to 2 position while driving in D

4

  (O/D)

or D

3

 , great driving force is applied to the clutch inside the transmis-

sion. Clutch operating pressure (line pressure) must be increased to
deal with this driving force.

During Shift Change

The line pressure is temporarily reduced corresponding to a change
in engine torque when shifting gears (that is, when the shift solenoid
valve is switched for clutch operation) to reduce shifting shock.

At Low Fluid Temperature

●

Fluid viscosity and frictional characteristics of the clutch facing change with fluid temperature. Clutch
engaging or band-contacting pressure is compensated for, according to fluid temperature, to stabilize
shifting quality.

●

The line pressure is reduced below 60

°C (140°F) to prevent

shifting shock due to low viscosity of automatic transmission
fluid when temperature is low.

●

Line pressure is increased to a maximum irrespective of the
throttle opening when fluid temperature drops to 

−10°C (14°F).

This pressure rise is adopted to prevent a delay in clutch and
brake operation due to extreme drop of fluid viscosity at low
temperature.

SHIFT CONTROL

The shift is regulated entirely by electronic control to accommodate vehicle speed and varying engine opera-
tions. This is accomplished by electrical signals transmitted by the revolution sensor and throttle position sen-
sor. This results in improved acceleration performance and fuel economy.

SAT004J

SAT005J

SAT006J

SAT007J

AT-180

[RE4R01A]

OVERALL SYSTEM

Control of Shift Solenoid Valves A and B

The TCM activates shift solenoid valves A and B according to sig-
nals from the throttle position sensor and revolution sensor to select
the optimum gear position on the basis of the shift schedule memo-
rized in the TCM.
The shift solenoid valve performs simple ON-OFF operation. When
set to ON, the drain circuit closes and pilot pressure is applied to the
shift valve.
[Relation between shift solenoid valves A and B and gear positions]

Control of Shift Valves A and B

Pilot pressure generated by the operation of shift solenoid valves A and B is applied to the end face of shift
valves A and B.
The drawing shows the operation of shift valve B. When the shift solenoid valve is “ON”, pilot pressure applied
to the end face of the shift valve overcomes spring force, moving the valve upward.

LOCK-UP CONTROL

The torque converter clutch piston in the torque converter is locked to eliminate torque converter slip to
increase power transmission efficiency. The solenoid valve is controlled by an ON-OFF duty signal sent from
the TCM. The signal is converted to oil pressure signal which controls the torque converter clutch piston.

Conditions for Lock-up Operation

When vehicle is driven in 4th gear position, vehicle speed and throttle opening are detected. If the detected
values fall within the lock-up zone memorized in the TCM, lock-up is performed.

SAT008J

Shift solenoid valve

Gear position

D

1

 , 2

1

 , 1

1

D

2

 , 2

2

 , 1

2

D

3

D

4

  (O/D)

N-P

A

ON (Closed)

OFF (Open)

OFF (Open)

ON (Closed)

ON (Closed)

B

ON (Closed)

ON (Closed)

OFF (Open)

OFF (Open)

ON (Closed)

SAT047J

Overdrive control switch

ON

OFF

Selector lever

D position

Gear position

D

4

D

3

Vehicle speed sensor

More than set value

Throttle position sensor

Less than set opening

Closed throttle position switch

OFF

A/T fluid temperature sensor

More than 40

°C (104°F)