Isuzu KB P190. Manual - part 1108

7A2-148   TRANSMISSION CONTROL SYSTEM (JR405E)

Valve Body Assembly

Legend

1. Oil filter
2. Pressure control (PC) solenoid valve
3. Low & reverse brake solenoid valve
4. High clutch solenoid valve
5. Torque converter clutch (TCC) solenoid valve
6. 2-4 brake solenoid valve
7. Low clutch solenoid valve

8. Low & reverse brake transmission fluid pressure

(TFP) switch

9. High clutch TFP switch

10. 2-4 brake TFP switch

11. Transmission fluid temperature (TFT) sensor

12. Lower body 
13. Upper body 

Employing the direct electronic control (Direct
Electronic Shift Control: DESC) for the clutch pressure
has simplified the oil pressure circuit, reduced the
number of functional components and made the control
valve compact. The control valve body is divided into
the upper body and the lower body. All solenoid valves,
the transmission fluid pressure (TFP) switch and the
transmission fluid temperature (TFT) sensor are
installed to the lower body. Three-way valve type
solenoid valves providing high responsibility are
employed. The pressure control (PC) solenoid valve is
switched between ON and OFF, and other solenoid

valves repeat ON and OFF at 50Hz (duty cycle). When
the solenoid valve is driven based on the signal from
the TCM, the fluid pressure is changed.

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-149

Legend

1. Pressure control (PC) solenoid valve
2. Low & reverse brake solenoid valve
3. High clutch solenoid valve
4. Torque converter clutch (TCC) solenoid valve
5. 2-4 brake solenoid valve 
6. Low clutch solenoid valve

Pressure Control (PC) Solenoid Valve 

The pressure control (PC) solenoid valve controls the
transmission fluid supply to the pressure regulator
spool valve in the valve body. The TCM controls the
solenoid valve by ON/ OFF signal based on the vehicle
running conditions. The TCM turns ON the solenoid
valve when a lower line pressure is required and turns
OFF when a higher line pressure is required. With the
operation of this solenoid valve, the operation and shift
of the hydraulic circuit in the transmission can be
performed smoothly. The PC solenoid valve is
controlled according to the range position, speed
sensor signals, transmission fluid temperature signal
and the accelerator pedal position signal.

Shift Solenoid Valve

Legend

1. Output port
2. Supply port
3. Drain port
4. Deenergized (commanded OFF)
5. Energized (commanded ON)

All shift solenoid valve is a duty cycle type, which is
turned ON and OFF at 50 Hz. The ration of ON and
OFF time can be freely controlled within 0 to 100%.
While no power is supplied, the solenoid valve supplies
output pressure. The low clutch solenoid valve adjusts
the low clutch pressure, the high clutch solenoid valve
adjusts the high clutch pressure, the 2-4 brake solenoid
valve adjusts the 2-4 brake pressure, and the low &
reverse brake solenoid valve adjusts the low & reverse
brake pressure respectively.

7A2-150   TRANSMISSION CONTROL SYSTEM (JR405E)

Torque Converter Clutch (TCC) Solenoid Valve

Legend

1. Output port
2. Drain port
3. Supply port 
4. Deenergized (commanded OFF)
5. Energized (commanded ON)

The torque converter clutch (TCC) solenoid valve is a
duty cycle type, which is turned ON and OFF at 50 Hz.
The ration of ON and OFF time can be freely controlled
within 5 to 95%. While no power is supplied, the
solenoid valve drains the output pressure. 

Transmission Fluid Pressure (TFP) Switch

Legend

1. High clutch TFP switch 
2. 2-4 brake TFP switch
3. Low & reverse brake TFP switch

Legend

1. Fluid pressure
2. Diaphram
3. Disc
4. Contact point 

The transmission fluid pressure (TFP) switch detects
the condition of the fluid pressure supply to the clutch
and brake, and then sends the result to the TCM. The
TFP switch is turned ON when the fluid pressure
reaches the switch working pressure, and turned OFF
when the fluid pressure decreases below the specified
value. The high clutch TFP switch detects the high
clutch fluid pressure, the 2-4 brake TFP switch detects
the 2-4 brake fluid pressure, and the low & reverse
brake TFP switch detects the low & reverse brake fluid
pressure respectively.

Transmission Fluid Temperature (TFT) Sensor

Legend

1. TFT sensor

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-151

The transmission fluid temperature (TFT) sensor is part
of the harness assembly. The sensor is a variable
resistor and it measures the temperature of the
transmission fluid. When the TFT sensor is cold, the
sensor resistance is high. When the transmission fluid
temperature increases, the sensor resistance
decreases. With high sensor resistance, the TCM
detects a high voltage on the signal circuit. With lower
sensor resistance, the TCM detects a lower voltage on
the signal circuit. 
If the fluid temperature increases to 135

°C (275°F), the

TCM illuminates A/T Oil Temp lamp on the instrument
panel cluster. When the fluid temperature deceases
below 125

°C (257°F), the lamp goes off. 

Transmission Range (TR) Switch

Legend

1. Input shaft speed (ISS) sensor
2. Output shaft speed (OSS) sensor
3. TR switch
4. In-line harness connector

The transmission range (TR) switch is connected to the
transmission manual shaft and installed externally to
the transmission case. The selector lever moves the
TR switch position via control cable. The TR switch
relays a signal to the TCM indicating transmission
range position by detecting ignition voltage through an
internal switch. Only one of the seven internal switches
will close for each P, R, N, D, 3, 2 and L position.
Normally, the TCM expects to detect one high voltage
input for each position.
The engine will not crank when the selector lever is at
any position other than the P or N range. 

Input Shaft Speed (ISS) Sensor

Legend

1. ISS sensor
2. Reverse & high clutch drum

The input shaft speed (ISS) sensor is located on right-
hand of the transmission case. The ISS sensor is a hall
effect element type sensor, which generates a square
wave signal pulse based on the reverse & high clutch
drum rotational speed (32 pulses per a rotation of the
reverse & high clutch drum that is fitted with the input
shaft by spline). The TCM calculates the turbine speed
by the ISS sensor signal, and uses it to calculate torque
converter slip speed and gear ratio. 

3

1

2

4

P

R

N

D

3

2

L

10

7

3

2

4

8

5

1

9

6

1

2