Isuzu KB P190. Manual - part 1067

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 

 

 

 

 

 

 

 

 

Input 

Accelerator Pedal 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 

 

 

 

 

 

 

 

 

 
 

7A1-30  CONSTRUCTION AND FUNCTION 

LINE PRESSURE CONTROL 

•

 The TCM drives the ON/OFF type line pressure solenoid based on the APP opening, vehicle speed, 

turbine rotational speed, ATF temperature and shift position signal. The ON/OFF type line pressure 
solenoid is actuated, and switches the line pressure to a high or low pressure number appropriate to the 
situation. 

•

  The line pressure generated by the oil pump acts on the point A of the pressure regulator valve.  When 

the pressure control solenoid is turned ON by the signal from the TCM, the solenoid pressure does not 
act.  The line pressure is adjusted to match the spring force acting on the right side of the pressure 
regulator valve. 

•

 When the pressure control solenoid is turned OFF, the solenoid pressure acts so that the line pressure is 

adjusted to match the spring force acting on the right side of the pressure regulator valve. 

•

 As a result, the line pressure is adjusted to be low when the pressure control solenoid is ON and to be 

high when the pressure control solenoid is OFF. 

•

 In position D, 3, 2 and L, the line pressure through the oil pressure circuit acts onto the point B of the 

pressure regulator valve.  The pressure regulator valve moves so as to increase the pressure to be 
drained, so that the line pressure is adjusted to be lower than the P, N, and R position by the difference of 
area at the point B. 

 
 

 

 

 Figure 50. Line Pressure Control 

 

LOCK-UP CONTROL 

•

 The lock-up solenoid adjusts the pressure and controls the lock-up based on the pre-set lock-up point, 

according to the vehicle speed, APP opening, engine rotations, turbine rotations and ATF temperature 
input signal, based on the signal from the TCM. 

•

 Smooth lock-up control is employed to engage or disengage the clutch smoothly at the time of lock-up on 

or off. 

•

 When the oil temperature is low (20

°

C or less), lock-up is disengaged even though the vehicle is at the 

lock-up speed. 

•

 The lock-up is disengaged also when the APP is closed. 

•

 When the TCM determines the lock-up engagement, the DUTY ratio to supply power to the lock-up 

solenoid is gradually increased (5% to 95%) and the oil between the lock-up piston and converter cover is 
gradually drained. 

CONSTRUCTION AND FUNCTION  7A1-31 

  As a result, the lock-up piston is fitted slowly to the converter cover under pressure securing smooth lock-

up engagement. 

 

 

 

 Figure 51. Lock-up Control 

 

DIRECT ELECTRIC SHIFT CONTROL (DESC) 

Feature  

•

 Based on each switch signal (low & reverse brake pressure, 2-4 brake pressure & high clutch pressure) 

and each sensor signal (turbine sensor, speed sensor, engine speed signal & APP position signal), the 
duty cycle type solenoid adjusts the clutch pressure to match the engine load and vehicle travel 
conditions. Controlling the engagement and disengagement of the clutch and brake pressure is directly 
and accurately controlled via TCM, which is different to the previous accumulator type. 

Operation 

•

 Instead of the previous system (on/off type of shift solenoid and shift valve), the combination of the duty 

cycle type solenoid and the amplifier (Amp) valve are used to adjust the clutch pressure to match the 
engine load and vehicle travel conditions, based on the signal from the TCM. Also, the pressure switch 
provided in the oil passage of the control valve transmits the oil pressure condition (at that time) to TCM, 
enabling the engagement and disengagement control of the clutch and brake to be directly and finely 
carried out. 

•

 When the gear is shifted from the 2nd to 3rd, 3rd to 4th (O/D), 4th (O/D) to 3rd and 3rd to 2nd, the clutch 

pressures on the engagement side and disengagement side are simultaneously controlled. 
As a result, engine racing or clutch drag is prevented which enables a smooth and quick shift response. 

 

7A1-32  CONSTRUCTION AND FUNCTION 

 

 
 
 

Direct Electric Shift Control 

 

 

 

 
 
 
 
 
 

Previous Model 

 

 

Figure 52. Direct Electric Shift Control (DESC)