2004 ISUZU TF SERIES engine oil
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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.
Page 3977 of 4264
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
Page 3979 of 4264
CONSTRUCTION AND FUNCTION 7A1-33
LEARNING CONTROL
Oil pressure control timing is optimally corrected at the time of clutch engagement and disengagement
and controlled to bring the speed-change time to the value preset to the TCM and compensate the
changes of the engine performance and changes of the transmission with time.
When the gear is shifted, the clutch pressure 2 is optimally corrected so that the speed-change time is as
near as the target value
1 preset to the TCM and the changes in the engine performance and the
changes of the transmission with time can be compensated based on the past speed-change results.
When the clutch is operated to shift the gear, the time of the clutch oil pressure release timing 4 on the
disengagement side is optimally corrected so that the changes of the engine rpm
3 is optimum.
Note:
When the battery terminal is disconnected, contents of learning are cleared and resultantly the speed
change shock may increase. After the vehicle has traveled, learning is repeated and the shock
decreases gradually.
Figure 53. Learning Control
Page 3980 of 4264
7A1-34 CONSTRUCTION AND FUNCTION
MAJOR INPUT/OUTPUT COMPONENT AND THEIR FUNCTIONS
Speed sensor Detects output shaft revolution and sends rpm signal to TCM.
Turbine sensor Detects input shaft revolution and sends rpm signal to TCM.
Engine speed sensor Inputs engine revolution from engine control computer.
Brake switch Detects brake pedal operated by the driver and sends signal to
TCM.
Inhibitor switch Detects select lever position and sends signal to TCM.
Mode select switch Detects "Power Drive" or "3rd Start" selected by the driver and
sends signal to TCM.
4L switch (4WD Only) Inputs 4L mode from transfer control computer.
ATF thermo sensor Detects ATF temperature and sends signal to TCM.
High clutch oil pressure switch Detects high clutch supply oil pressure and sends signal to
TCM.
2-4 brake oil pressure switch Detects 2-4 brake supply oil pressure and sends signal to
TCM.
Low & Reverse brake oil pressure switch Detects low & reverse brake supply oil pressure and signal to
TCM.
Throttle position sensor Inputs throttle opening angle from engine control computer.
Input
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.
Line pressure solenoid Regulates oil pump delivery pressure to the appropriate line
pressure for current driving condition based on signal from
TCM.
Low clutch solenoid Selects appropriate gear shifting position for current driving
condition and regulates low clutch supply oil pressure based on
signal from TCM.
High clutch solenoid Selects appropriate gear shifting position for current driving
condition and regulates high clutch supply oil pressure based
on signal from TCM.
2-4 brake solenoid Selects appropriate gear shifting position for current driving
condition and regulates 2-4 brake supply oil pressure based on
signal from TCM.
Low & Reverse brake solenoid Selects appropriate gear shifting position for current driving
condition and regulates low & reverse brake supply oil
pressure based on signal from TCM.
Lock-up solenoid Regulates lock-up pressure to appropriate level for current
driving conditions based on signal from TCM.
Mode indicator lamp Indicates POWER DRIVE or 3rd START switch position.
Speed meter signal (2WD Only) Outputs vehicle speed to speed meter.
A/T OIL TEMP indicator lamp Indicates A/T OIL TEMP indicator lamp in case of high
temperature.
Output
CHECK TRANS indicator lamp Indicates CHECK TRANS indicator lamp in case of
malfunction.
Page 3981 of 4264
CONSTRUCTION AND FUNCTION 7A1-35
CONTROL CIRCUIT BLOCK DIAGRAM
Speed sensor
Turbine sensor
Brake switch
Inhibitor switch
Power drive, 3rd start
switch
ATF oil thermo sensor
High clutch oil pressure
switch
2-4 brake oil pressure
switch
Low & reverse brake oil
pressure switch
Transfer control module
(4WD Only)
Engine Control Module
(ECM)
Line pressure solenoid
Low clutch solenoid
High clutch solenoid
2-4 brake solenoid
Low & reverse brake
solenoid
Lock-up solenoid
ATF temperature
indicator lamp
Speed meter (2WD
Only)
Power, 3rd start indicator
lamp
Check trans indicator
lamp
Data link connector Self-diagnosis
function
Transmission
Control
Module
(TCM)
4L mode
Engine
speed
Throttle
angle
Figure 54. Control Circuit Block Diagram
Page 3996 of 4264
7A2-4 DIAGNOSIS (JR405E)
PAGE
NO. D3: GEAR SHIFT POINT IS LOW OR HIGH AT ALL POINT................................. 7A2-120
NO. D4: GEAR SHIFT POINT IS LOW OR HIGH AT LIMITED POINT ......................... 7A2-120
NO. D5: NO KICK-DOWN .............................................................................................. 7A2-120
NO. E1: NO GEAR SHIFT .............................................................................................. 7A2-121
NO. E2: ONLY 4TH GEAR (O/D) IS NOT SELECTABLE ............................................. 7A2-124
NO. E3: GEAR IS SHIFTED 2ND TO 3RD IN 2 RANGE ............................................... 7A2-126
NO. E4: GEAR IS SHIFTED 1ST TO 2ND IN L RANGE................................................ 7A2-126
NO. E5: GEAR IS SHIFTED 3RD TO 4TH IN 3 RANGE................................................ 7A2-126
NO. F1: LOW MAXIMUM SPEED OR POOR ACCELERATION ................................... 7A2-127
NO. F2: ENGINE RACES UP DURING ACCELERATION (SLIP) ................................. 7A2-130
NO. F3: NOISE OR VIBRATION DURING THE RUNNING IN R, D, 3, 2 OR L
RANGE .......................................................................................................................... 7A2-130
NO. F4: ENGINE BRAKE DOES NOT APPLY IN L RANGE......................................... 7A2-130
NO. F5: ENGINE STALLS BEFORE VEHICLE STOPS FROM RUNNING ................... 7A2-131
NO. G1: VEHICLE MOVES IN P RANGE OR PARKING GEAR IS NOT
DISENGAGED OTHER THAN P RANGE ..................................................................... 7A2-131
NO. G2: CREEP FORCE IS LARGE.............................................................................. 7A2-131
NO. G3: CREEP FORCE IS SMALL .............................................................................. 7A2-132
NO. G4: LARGE NOISE DURING IDLING WITH THE VEHICLE IN STOP STATE ...... 7A2-133
NO. H1: JUDDER OCCURS AT THE LOCK-UP ........................................................... 7A2-133
NO. H2: LARGE LOCK-UP SHOCK .............................................................................. 7A2-133
NO. H3: LOCK-UP POINT IS HIGH OR LOW ............................................................... 7A2-133
NO. I1: NO LOCK-UP .................................................................................................... 7A2-134
NO. J1: OIL LEAKS FROM BREATHER ....................................................................... 7A2-136
NO. J2: OIL LEAKS BETWEEN ENGINE AND CONVERTER HOUSING .................... 7A2-136
NO. J3: OIL LEAKS BETWEEN MAIN CASE AND CONVERTER HOUSING.............. 7A2-136
NO. J4: OIL LEAKS BETWEEN MAIN CASE AND REAR HOUSING .......................... 7A2-136
NO. J5: OIL LEAKS FROM OIL PAN ............................................................................ 7A2-136
NO. J6: OIL LEAKS FROM MANUAL SHAFT OIL SEAL ............................................. 7A2-136
NO. J7: OIL LEAKS FROM OIL COOLER PIPE JOINT................................................ 7A2-136
NO. Z1: TRANSMISSION OVERHEAT .......................................................................... 7A2-136
NO. Z2: MODE LAMP (POWER DRIVE OR 3RD START) DOES NOT LIGHT UP
WHEN THE POWER MODE OR 3RD START MODE IS TURNED ON........................ 7A2-137
Page 4034 of 4264
7A2-42 DIAGNOSIS (JR405E)
DTC P0710 (Flash Code 15) ATF Temperature Sensor Failure
ATF
Temp.
Sensor
TCM
B4 (+)
B14 (-)
H23 (8)
(3)
C95 (4)
(14)
BLU
Terminal
Assembly
BLU/BLKE54 (2)
(8)
BLU
BLU/BLK
Setting Condition:
The condition in which the voltage of oil temperature sensor is below 0.1V (146 C) and ATF temperature
warning lamp ON in the P or N range lasts for more than 5 minutes.
Or
The vehicle speed exceeds 20 km/h and the voltage of oil temperature sensor exceeds 2.43V (-40 C) for more
than 10 seconds.
Fail Safe:
The lock-up is inhibited, and TCM is controlled ATF temperature 80 C condition as substitute.
When the engine speed is more than 470 rpm for 10 minuets, the lock-up and gear shift to 4th (over-drive) are
allowed.
Possible Cause:
Oil temperature sensor wire open circuit or short circuit.
Oil temperature sensor malfunction.
Power supply wire open circuit, short circuit to battery or short circuit to ground between oil temperature sensor
and TCM terminal B4 (C95).
Ground wire open circuit or short circuit to battery between oil temperature sensor terminal and TCM terminal
B14 (C95).
Poor connection of each connector.
Reference:
Following output voltage and resistance can be measured by circuit tester.
Measurement terminal: B4 (C95) and B14 (C95)
ATF Temperature Output Voltage Resistance ATF Temperature Output Voltage Resistance
20 C 1.55V 2,500 80 C 0.5V 320
40 C 1.08V 1,160 100 C 0.3V 190
60 C 0.7V 590 120 C 0.2V 120
Page 4058 of 4264
7A2-66 DIAGNOSIS (JR405E)
Step Action Yes No
1 Clear the DTC from the memory once.
Was the action complete?
Go to Step 2
Refer DTC clear
method in this
manual.
2 Turn the ignition switch off once, then restart the engine and shift to
4th gear in the D range. When about 10 seconds elapsed, does the
CHECK TRANS lamp blink?
Go to Step 3 Go to Step 7
3 Is the DTC P0753 (31) Low & Reverse Brake Duty Solenoid Failure
stored? Go to P0753 (31)
Section Go to Step 4
4 Connect the Tech 2 and select the item for low & reverse brake
pressure switch. Is the indication of low & reverse brake pressure
switch turned off when the terminal assembly connector is
disconnected?
Go to Step 5
Repair the harness
or connector.
Go to Step 12
5 Turn the key switch off and disconnect the terminal assembly
connector. Are the pins correct?
Go to Step 6
Repair the
connector or pin.
Go to Step 12
6 Remove the oil pan. Is the continuity correct between terminal
assembly terminal 12 and low & reverse brake pressure switch
connector?
12
Repair the harness
or connector.
Go to Step 12
Replace pressure
switch.
Go to Step 12
7 Start the engine and select the R range. When about 10 seconds
elapsed, does the CHECK TRANS lamp blink?
Go to Step 8
Go to P0753 (31)
Section
8 Connect the Tech 2, and with the key switch in OFF position, short
the terminals 11 and 12 on the vehicle harness side. Does the
indication of the low & reverse brake pressure switch on the Tech 2
becomes on when the key switch is turned on?
Go to Step 9
Repair the harness
or connector.
Go to Step 12