2008 NISSAN LATIO engine

AT-22
< SERVICE INFORMATION >
A/T CONTROL SYSTEM
“D1” and “21” Positions
*: Overrun clutch remains in engaged condition when throttle opening is less than 1/16.•Forward clutch
•Forward one-way clutch
•Overrun clutch
•Low & reverse brakeAs overrun clutch engages, rear internal gear is locked by the operation of low and re-
verse brake.
This is different from that of D
1 and 21.
Engine brake Overrun clutch always engages, therefore engine brake can be obtained when deceler-
ating.
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•Forward one-way clutch
•Forward clutch
•Low one-way clutchRear internal gear is locked to rotate counterclockwise because of the functioning of these three
clutches.
Overrun clutch
engagement conditions
(Engine brake)D
1: OD OFF (OD OFF indicator lamp is on) and throttle opening is less than specification*
2
1: Always engaged
At D
1 and 21 positions, engine brake is not activated due to free turning of low one- way clutch.

A/T CONTROL SYSTEM
AT-25
< SERVICE INFORMATION >
D
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P “D
4” (OD) Position
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•High clutch
•Brake band
•Forward clutch (Does not affect power
transmission)Input power is transmitted to front carrier through high clutch.
This front carrier turns around the sun gear which is fixed by brake band and makes
front internal gear (output) turn faster.
Engine brakeAt D
4 position, there is no one-way clutch in the power transaxle line and engine brake
can be obtained when decelerating.

AT-26
< SERVICE INFORMATION >
A/T CONTROL SYSTEM
“R” Position
SAT380J
•Reverse clutch
•Low & reverse brakeFront planetary carrier is stationary because of the operation of low and reverse brake.
Input power is transmitted to front sun gear through reverse clutch, which drives front
internal gear in the opposite direction.
Engine brakeAs there is no one-way clutch in the power transaxle line, engine brake can be obtained
when decelerating.

A/T CONTROL SYSTEM
AT-27
< SERVICE INFORMATION >
D
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TCM FunctionINFOID:0000000001703163
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 transaxle senses vehicle operating conditions through various sensors or signals. It always
controls the optimum shift position and reduces shifting and lock-up shocks.
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SWITCHES & SENSORS
⇒TCM
⇒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
Turbine revolution sensor (Power
train revolution sensor)
Vehicle speed sensor
Overdrive control switch signal
Stop lamp switch signalShift control
Line pressure control
Lock-up control
Overrun clutch control
Fail-safe control
Self-diagnosis
CONSULT-III communication
line controlShift solenoid valve A
Shift solenoid valve B
Overrun clutch solenoid valve
Torque converter clutch solenoid
valve
Line pressure solenoid valve
OD OFF indicator lamp

AT-28
< SERVICE INFORMATION >
A/T CONTROL SYSTEM
CONTROL SYSTEM DIAGRAM
CAN CommunicationINFOID:0000000001703164
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-6,
"System Description".
Input/Output Signal of TCMINFOID:0000000001703165
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Control itemLine
pressure
controlVehicle
speed
controlShift
controlLock-up
controlEngine
brake
controlFail-safe
functionSelf-diag-
nostics
function
InputAccelerator pedal position signal
(*5)XXXXX(*3) XX
Vehicle speed sensor·A/T
(Revolution sensor)XXXXX(*3) XX
Vehicle speed sensor·MTR (*1) X (*1) X (*1) X (*1) X X
Closed throttle position signal
(*5)(*2) X (*2) X X X (*4) X
Wide open throttle position signal
(*5)(*2) X (*2) X (*4) X
Turbine revolution sensor (Power
train revolution sensor)XXXXX
Engine speed signal X X X X
PNP switch XXXXX(*3) X(*4) X
Stop lamp switch signal
(*5)XX (*4) X
A/T fluid temperature sensors
(*5)XXXX XX
Overdrive control switch signal
(*5)XXXX (*4) X
TCM power supply voltage signal X X X X

A/T CONTROL SYSTEM
AT-29
< SERVICE INFORMATION >
D
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*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-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 ControlINFOID:0000000001703166
• TCM has various line pressure control characteristics to match 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 characteristic of the line pressure to the throttle opening is set
for suitable clutch operation.
BACK-UP CONTROL (ENGINE BRAKE)
If the selector lever is shifted to “2” position while driving in D4 or D3,
great driving force is applied to the clutch inside the transaxle. Clutch
operating pressure (line pressure) must be increased to deal with
this driving force.
DURING SHIFT CHANGE
Out-
putShift solenoid valve A/B X (*3) X X
Line pressure solenoid X (*3) X X
Torque converter clutch solenoid
valveX(*3) XX
Overrun clutch solenoid valve X X (*3) X X
OD OFF indicator lamp
(*6)XX Control itemLine
pressure
controlVeh icl e
speed
controlShift
controlLock-up
controlEngine
brake
controlFail-safe
functionSelf-diag-
nostics
function
SAT003J
SAT004J

AT-30
< SERVICE INFORMATION >
A/T CONTROL SYSTEM
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
• A/T fluid viscosity and frictional characteristics of the clutch facing change with A/T fluid temperature. Clutch
engaging or band-contacting pressure is compensated for, according to A/T fluid temperature, to stabilize
shifting quality.
• The line pressure is reduced below 60°C (140°F) to prevent shift-
ing shock due to high viscosity of A/T fluid when temperature is
low.
• Line pressure is increased to a maximum irrespective of the throt-
tle opening when A/T 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 A/T fluid viscosity at low temper-
ature.
Shift ControlINFOID:0000000001703167
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 the ECM (accelerator
pedal position sensor). This results in improved acceleration performance and fuel economy.
CONTROL OF SHIFT SOLENOID VALVES A AND B
The TCM activates shift solenoid valves A and B according to sig-
nals from the accelerator pedal position sensor and revolution sen-
sor to select the optimum gear position on the basis of the shift
schedule memorized 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
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AT-32
< SERVICE INFORMATION >
A/T CONTROL SYSTEM
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 drain-
ing the torque converter clutch piston applying pressure and the torque converter clutch piston release pres-
sure is generated.
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 generating
the torque converter clutch piston applying pressure and the torque converter clutch piston release pressure is
drained.
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 steadily increase the
torque converter clutch solenoid pressure.
In this way, the lock-up applying pressure gradually rises and while the torque converter clutch piston is put
into half-clutched status, the torque converter clutch piston applying pressure is increased and the coupling is
completed smoothly.
Engine Brake Control (Overrun Clutch Control)INFOID:0000000001703169
Forward one-way clutch is used to reduce shifting shocks in downshifting operations. This clutch transmits
engine torque to the wheels. However, drive force from the wheels is not transmitted to the engine because
the one-way clutch rotates idle. This means the engine brake is not effective.
The overrun clutch operates when the engine brake is needed.
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