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)
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