Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual — part 1841

7A1-26 CONSTRUCTION AND FUNCTION

CONTROL MECHANISM

CONTENT OF FUNCTION AND CONTROL

Item

Description

Line pressure control

TCM issues a signal according to the vehicle traveling, engine load and other conditions to
TCM and the ON/OFF type line pressure solenoid is driven to switch the line pressure to
high or low pressure.
The line pressure solenoid is switched to the low pressure side when the solenoid is turned
ON (power supplied) and to the high pressure side when turned OFF (no power supplied).
In the forward travel range (D, 3, 2, L range), the line pressure decreases lower than that in
the P, N, and R range through the oil pressure circuit for the forward travel range.

Gear shift control

The TCM issues a shift solenoid drive signal based on the traveling mode switch, inhibitor
switch, vehicle speed, throttle opening and other input signal to control the optimum gear
position automatically.
Speed change features have been set up to the TCM; the normal mode is suited to usual
traveling and the power mode is appropriate when the vehicle is loaded or accelerates the
speed.
In addition, speed change features used only for high oil temperature, hill climbing, and
down have been set up to the TCM, which are automatically switched depending on the
traveling conditions.
When the oil temperature is low (below 10

°

C), speed change from the third to the fourth

speed is prohibited by the gear shift control.

Shift pattern selection
control

According to a vehicle condition, the TCM selects the following shift pattern.

Selection

Priority

Shift Pattern

3rd Start

Lamp

Power Drive

Lamp

High

High Temperature

OFF

OFF

3rd Start

ON

4L

Power SW Off

OFF

Down Slop

Power SW On

Power

ON

Up Slope

Low

Normal

OFF

OFF

- High temperature mode -

High temperature mode setting condition
ATF temperature: More than 123

°

C

Above condition is met for more than 10 seconds.
High temperature mode cancel condition
ATF temperature: Less than 116

°

C

Above condition is met for more than 10 seconds.

- 3rd start mode -

3rd start mode setting condition
3rd start switch: On

→

Off (Pushed)

Vehicle speed: Less than 11km/h
ATF temperature: Less than 115

°

C

Throttle position: Less than 8%
Select lever position: D range
Above conditions are met at the same time.
3rd start mode reset condition
3rd start switch: On

→

Off again(Pushed again)

Vehicle speed: More than 34km/h
Select lever position: Other than D range
At least, one of above conditions is met.

CONSTRUCTION AND FUNCTION 7A1-27

Item

Description

- 4L mode -

4L mode setting condition
‚

L switch: On

Vehicle speed: More than 5km/h
Above conditions are met at the same time.
4L mode reset condition
4L switch: Off
Vehicle speed: Less than 4km/h
Above conditions are met at the same time.

- Down slope mode -
Down slope mode setting condition
Brake switch: On
Engine idle condition: More than 2.5 seconds
Select lever position: D or 3 range
Vehicle speed: More than 55km/h
Vehicle speed change: +1km/h
Above conditions are met at the same time.
Down slope mode reset condition
Engine idle condition: Not idle condition
Select lever position: Other than D or 3 range
At least, one of above conditions is met.

- Power Mode -

When power drive switch is On at only D range, 3 range and 2 range, the shift change is
performed by 1

– 4 speed based on shift diagram set as power pattern

.

- Up slope mode -
TCM compares up slope reasoning value calculated from average throttle angle with one
calculated from average acceleration, regards smaller value as up slope.
And up slope reasoning value is calculated from present vehicle speed.

TCM compares the former with the latter judges as up slope mode, when the former is
bigger than latter.

Lock-up control

The lock-up solenoid adjusts the pressure based on the signal from the TCM according to
the vehicle speed, throttle opening and other input signals based on the pre-set lock-up
point to control the lock-up.
Smooth lock-up control engages and disengages the clutch smoothly at the time of lock-up.
When the oil temperature is low (below 20

°

C) or high (above 128

°

C), lock-up is prohibited

even when the vehicle is at a lock-up speed.
The lock-up is disengaged also when the throttle is closed.

Direct electronic shift
control (DESC)

The duty cycle type solenoid is used for each clutch and brake. The solenoid adjusts the
clutch pressure to be suited to the engine load and vehicle traveling condition based on the
signal from the TCM. The pressure switch provided in the control valve oil passage sends
the oil pressure condition to the TCM to control the disengagement and engagement of the
clutch and brake directly and finely.

Learning control

Learning is controlled to correct the oil pressure control timing to engage or disengage the
clutch optimally in order to compensate changes of the engine performance and changes
of the transmission with time. It is controlled to bring the speed-change time closer to the
value pre-set to the TCM.

7A1-28 CONSTRUCTION AND FUNCTION

Item

Description

Fail-safe function

In case of malfunction of the vehicle speed sensor, throttle position sensor, all solenoids or
inhibitor switch, TCM automatically begins fail-safe control to minimize effects on driving.

The gear is fixed at the 3rd-speed position and power supply to the solenoid is shut off so
that the solenoid does not work nor lock up.

Self-diagnosis function

Parts required for controlling the automatic transmission are provided with a self-diagnosis
function. When any trouble occurs, the check trans indicator lamp blinks to warn the driver.
The trouble code is memorized in the TCM.

CONSTRUCTION AND FUNCTION 7A1-29

CONTROL ITEM, INPUT AND OUTPUT

Control item

Item

Line

pressure

control

Gear

shift

control

Shift

pattern

selection

Lock-up

control

Direct

electronic

shift

control

(DECS)

Learning

control

Fail-safe

function

Self-

diagnosis

function

Speed sensor

Turbine sensor

Engine speed sensor

Brake switch

Inhibitor switch

Mode select switch

4L switch (4WD Only)

ATF thermo sensor

High clutch oil pressure switch

2-4 brake oil pressure switch

Low & Reverse brake oil pressure
switch

In

put

Throttle position sensor

Line pressure solenoid

Low clutch solenoid

High clutch solenoid

2-4 brake solenoid

Low & Reverse brake solenoid

Lock-up solenoid

Shift pattern indicator lamp

ATF temperature indicator lamp

O

u

tput

Check trans indicator lamp