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.