Isuzu KB P190. Manual — part 1066

CONSTRUCTION AND FUNCTION 7A1-25

TRANSMISSION CONTROL MODULE (TCM)

•

The TCM is fitted on the side of the brake pedal via two stud bolts.

•

The TCM judges the line pressure, gear shifting point and lock-up operation based on electrical signals

from switches and sensors, and sends the appropriate signals to solenoids.

B9 B8 B7 B6 B5 B4 B3 B2 B1

A9

A8 A7 A6 A5 A4 A3 A2 A1

B18 B17 B16 B15 B14 B13 B12 B11 B10

A18 A17 A16 A15 A14 A13 A12 A11 A10

B24 B23 B22

B21 B20 B19

A24 A23 A22

A21 A20 A19

Connect to White Connector Connect to Grey Connector

Figure 49. Pin Assignment

Pin No.

Pin Assignment

Pin No.

Pin Assignment

B1

2-4 Brake Oil Pressure Switch

A1

V BATT (Battery Back-up Power Supply)

B2

2 Position Switch

A2

P Position Switch

B3

Turbine Sensor

A3

Brake Switch

B4

ATF Thermo Sensor

A4

3rd Start Indicator Lamp

B5

Ground

A5

K-Line Signal (Tech 2 Serial Communication)

B6

Low & Reverse Brake Duty Solenoid

A6

No Connection

B7

2-4 Brake Duty Solenoid

A7

Engine Speed Sensor

B8

High Clutch Duty Solenoid

A8

No Connection

B9

Low Clutch Duty Solenoid

A9

No Connection

B10

N Position Switch

A10

Vehicle Speed Sensor Out (2WD Only)

B11

D Position Switch

A11

3rd START Select Switch

B12

Low & Reverse Brake Oil Pressure Switch

A12

4L Mode Switch (4WD Only)

B13

Vehicle Speed Sensor

A13

No Connection

B14

ATF Thermo Sensor Ground

A14

No Connection

B15

No Connection

A15

No Connection

B16

No Connection

A16

Accelerator Pedal Position Sensor

B17

Lock-up Duty Solenoid

A17

3 Position Switch

B18

Vign (Ignition Power Supply)

A18

DIAG Switch (Test Switch)

B19

R Position Switch

A19

A/T OIL TEMP Indicator Lamp

B20

High Clutch Oil Pressure Switch

A20

CHECK TRANS Indicator Lamp

B21

L Position Switch

A21

POWER DRIVE Indicator Lamp

B22

Ground (Shift Solenoid)

A22

No Connection

B23

Line Pressure Solenoid

A23

No Connection

B24

Vign (Ignition Power Supply)

A24

POWER DRIVE Select Switch

7A1-26 CONSTRUCTION AND FUNCTION

CONTROL MECHANISM

CONTENT OF FUNCTION AND CONTROL

Item

Description

Line pressure control

TCM issues a signal according to vehicle travel, engine load and other conditions, which
drives the ON/OFF type line pressure solenoid 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 position (D, 3, 2, L position), the line pressure decreases lower than
that in the P, N, and R position through the oil pressure circuit.

Gear shift control

The TCM issues a shift solenoid drive signal based on the traveling mode switch, inhibitor
switch, the vehicle speed, the APP opening and other input signals, to control the optimum
gear position automatically.
Shift features have been set up to the TCM; the normal mode is suited to normal travel, and
the power mode is used when the vehicle is loaded or the speed accelerated.
In addition, shift features used only for high oil temperature, hill climbing, and downward
travel have been set up to the TCM. These are automatically switched depending on the
travel conditions.
When the oil temperature is low (10

°

C or less), shifting up from the third speed to the fourth

speed is prohibited by the gear shift control.

Shift pattern selection
control

The TCM selects the following shift pattern according to a vehicle condition.

Selection

Priority

Shift Pattern

3rd Start

Lamp

Power Drive

Lamp

High

High Temperature

OFF OFF

3rd Start

ON

4L

Power SW Off

OFF

Down Slope

Power SW On

Power

ON

Up Slope

Low

Normal

OFF

OFF

- High temperature mode -

High temperature mode setting condition
ATF temperature: 122

°C or more

Above condition is met for 10.16 seconds.
High temperature mode cancel condition
ATF temperature: 115

°C or less

Above condition is met for 10.16 seconds.

-NOTE-

High temperature mode may be activated with driving conditions other than the setting
conditions stated, in order to protect Automatic Transmission from thermal damage.

- 3rd start mode -

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

→ Off (Pushed)

Vehicle speed: 11km/h or less.
ATF temperature: 115

°C or less.

APP position: 8% or less.
Select lever position: D position
Above conditions are all met at the same time.

CONSTRUCTION AND FUNCTION 7A1-27

Item

Description

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

→ Off again(Pushed again)

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

- 4L mode -

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

- Down slope mode -
Down slope mode setting condition
Brake switch: On
Accelerator pedal condition: Released for 2 seconds or more.
Select lever position: D or 3 position
Vehicle speed: More than 60km/h
Increment of vehicle speed: More than 1km/h per second
Above conditions are all met at the same time.
Down slope mode reset condition
Accelerator pedal condition: Depressed
Select lever position: Other than D or 3 position
At least, one of above conditions is met.

- Power Mode -

When the power drive switch is On the shift pattern change is performed by 1

– 4 speed

based on shift diagram set as power pattern

.

- Up slope mode -
Up-slope reasoning value is calculated from the average APP angle and the average
acceleration. Otherwise, up-slope reasoning value is calculated from the vehicle speed.

TCM chooses up-slope mode when the former is bigger than the latter.

Lock-up control

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

°

C or less), lock-up is prohibited even when the vehicle

is at a lock-up speed.
The lock-up is also disengaged when the APP 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 suit 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, which controls the disengagement or engagement of the
clutch and brake directly and finely.

7A1-28 CONSTRUCTION AND FUNCTION

Item

Description

Learning function

The learning function is provided 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 shift time closer to
the value pre-set to the TCM.

Fail-safe function

In the case of a malfunction of the vehicle speed sensor, APP sensor, all solenoids or the
inhibitor switch, TCM automatically begins fail-safe control to minimize effects on driving.
The gear is fixed in 3rd gear and the power supply to the solenoid is shut off so that the
solenoid does not work. Lock up clutch is disengaged in this mode.

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.