2004 ISUZU TF SERIES switch

7A1-24 CONSTRUCTION AND FUNCTION
BRAKE SWITCH

The brake switch is installed to the brake pedal. When the driver steps on the brake pedal, an electric
signal is sent to the TCM.



Brake Switch
Accelerator Pedal
Brake Pedal



TCM A3 +12V
Figure 45. Brake Switch Figure 46. Pin Assignment


MODE SELECT SWITCH

The mode select switch is installed beside the select lever. When the driver selects the PWR or 3rd, an
electric signal is sent to the respectively. It turns ON the indicator lamp in the meter.

The 3rd START mode can be used only in the D range.

Mode Select Switch
Gear Select Lever









Power 3rd Illumination
Lamp
1 (Illumination)
2 (Ground)
3 (TCM A24)
4 (No Connection)
5 (TCM A11)
6 (Ground)

21
65 4 3
Figure 47. Mode Select Switch Figure 48. Pin Assignment

CONSTRUCTION AND FUNCTION 7A1-25
TRANSMISSION CONTROL MODULE (TCM)

The TCM is fitted side of brake pedal by means of two stud bolts.

The TCM judges necessary line pressure, gear shifting point and lock-up operation based on electrical
signals from switches and sensors and sends appropriate signals to solenoids.















        




















 
 
 
 
 
 
 












      
  

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 Range Switch A2 P Range 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 Range Switch A10 Vehicle Speed Sensor Out (2WD Only)
B11 D Range 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 Ground A15 No Connection
B16 No Connection A16 Throttle Position Sensor
B17 Lock-up Duty Solenoid A17 3 Range Switch
B18 Vign
Ignition Power Supply) A18 DIAG Switch (Test Switch)
B19 R Range Switch A19 A/T OIL TEMP Indicator Lamp
B20 High Clutch Oil Pressure Switch A20 CHECK TRANS Indicator Lamp
B21 L Range 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 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
4L 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: More than 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 or 3 range, the shift 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 throttle angle and the average
acceleration. Otherwise, up-slope reasoning value is calculated from the vehicle speed.
TCM 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
controlDirect
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
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

Output
Check trans indicator lamp

7A1-30 CONSTRUCTION AND FUNCTION
LINE PRESSURE CONTROL

Either the throttle opening, vehicle speed, turbine rotational speed, ATF temperature or speed-change
range signal appropriate under the situation is issued from the TCM. The ON/OFF type line pressure
solenoid is actuated and switches the line pressure to high or low pressure.

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 the D, 3, 2 and L range, the line pressure through the oil pressure circuit acts onto the point B of the
pressure regulator valve and 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 range 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, throttle 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.

When the oil temperature is low (below 20C) or high (over 128C), lock-up is disengaged even though
the vehicle is at the lock-up speed.

The lock-up is disengaged also when the throttle 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.
As a result, the lock-up piston is fitted slowly under pressure to the converter cover securing smooth lock-
up engagement.

CONSTRUCTION AND FUNCTION 7A1-31


Figure 51. Lock-up Control

DIRECT ELECTRIC SHIFT CONTROL (DESC)
Feature

Based on the each switch signals (low & reverse brake pressure, 2-4 brake pressure & high clutch
pressure) and sensors signals (turbine sensor, speed sensor, engine speed signal & throttle position
signal), duty cycle type solenoid adjusts the clutch pressure to match the engine load and vehicle
traveling condition. By this result, controlling the engagement and disengagement of the clutch and brake
pressure is directly and accurately controlled via TCM, which is not realized in previous accumulator type.
Operation

Instead of the previous system (on/off type of shift solenoid and shift valve), the combination of duty cycle
type solenoid and amplifier (Amp) valve are used to adjust the clutch pressure to match the engine load
and vehicle traveling condition based on the signal from the TCM, and the pressure switch provided in the
oil passage of the control valve transmits the oil pressure condition at that time to TCM, thus controlling
the engagement and disengagement of the clutch and brake directly and finely.

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
pressure on the engagement side and that on the disengagement side are simultaneously controlled.
As a result, engine racing or clutch drag is prevented securing smooth and quick speed change response