switch ISUZU TF SERIES 2004 Workshop Manual

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

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.

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

CONSTRUCTION AND FUNCTION 7A1-37
COMPONENT AND THEIR OPERATING CONDITION

Clutch Brake Solenoid Pressure Switch
Select
lever
position
Gear
position
Gear
Shift
Lock-
up
L/C
H/C
R/C
L/O.C
L&R/B
2-4/B
L/C.S
H/C.S
L&R/
B.S
2-4/
B.S
L/U.S H/
C.P/
SWL&R/
B.P/
SW2-4
B.P/
SW
P - -

R Reverse -

N - -

1st

2nd
3rd


D
4th

1st

2nd
3rd


3
4th(*1)


1st

2nd

3rd(*1)



2
4th(*1)


1st
2nd(*1)

3rd(*1)



L
4th(*1)



*1:Transmission is shifted at high speed to prevent engine over-run.
- Engaged or operated
- Operative when accelerating

DIAGNOSIS (JR405E) 7A2-1
SECTION 7A2
DIAGNOSIS
TABLE OF CONTENTS
PAGE
BASIC TROUBLE SHOOTING..................................................................................................7A2-6
CHECK TRANS INDICATOR & SELF DIAGNOSIS..............................................................7A2-7
DIAGNOSIS WITH TECH 2........................................................................................................7A2-9
TECH 2 CONNECTION .................................................................................................. 7A2-9
TECH 2 OPERATING FLOW CHART (START UP)..............................................................7A2-10
TYPICAL SCAN DATA................................................................................................................7A2-13
MISCELLANEOUS TEST...........................................................................................................7A2-14
INTERMITTENT DIAGNOSIS....................................................................................................7A2-16
SNAPSHOT DISPLAY WITH TIS 2000....................................................................................7A2-17
SERVICE PROGRAMMING SYSTEM (SPS) ................................................................. 7A2-21
CIRCUIT DIAGRAM.....................................................................................................................7A2-24
PART LOCATION........................................................................................................................7A2-26
CONNECTOR LIST.....................................................................................................................7A2-31
DIAGNOSIS TROUBLE CODE TABLE...................................................................................7A2-33
FAIL-SAFE FUNCTION..............................................................................................................7A2-35
DTC P0722 (FLASH CODE 11) VEHICLE SPEED SENSOR NO SIGNAL......................7A2-36
DTC P0727 (FLASH CODE 13) ENGINE REVOLUTION SENSOR NO SIGNAL............7A2-38
DTC P0717 (FLASH CODE 14) TURBINE SPEED SENSOR NO SIGNAL......................7A2-40
DTC P0710 (FLASH CODE 15) ATF TEMPERATURE SENSOR FAILURE....................7A2-42
DTC P0560 (FLASH CODE 16) SYSTEM VOLTAGE FAILURE........................................7A2-43
DTC P0705 (FLASH CODE 17) INHIBITOR SWITCH FAILURE........................................7A2-44
DTC P1120 (FLASH CODE 22) THROTTLE SIGNAL FAILURE........................................7A2-46
DTC P1875 (FLASH CODE 25) GND RETURN CIRCUIT FAILURE.................................7A2-47
DTC P0753 (FLASH CODE 31) LOW & REVERSE BRAKE DUTY
SOLENOID FAILURE................................................................................................................7A2-48
DTC P0758 (FLASH CODE 32) 2-4 BRAKE DUTY SOLENOID FAILURE......................7A2-51
DTC P0763 (FLASH CODE 33) HIGH CLUTCH DUTY SOLENOID FAILURE................7A2-54
DTC P0768 (FLASH CODE 34) LOW CLUTCH DUTY SOLENOID FAILURE................7A2-57

7A2-2 DIAGNOSIS (JR405E)
PAGE
DTC P0748 (FLASH CODE 35) LINE PRESSURE SOLENOID FAILURE.......................7A2-60
DTC P1860 (FLASH CODE 36) LOCK-UP DUTY SOLENOID FAILURE.........................7A2-62
DTC P1853 (FLASH CODE 26) LOW & REVERSE BRAKE PRESSURE
SWITCH FAILURE......................................................................................................................7A2-64
DTC P1858 (FLASH CODE 27) 2-4 BRAKE PRESSURE SWITCH FAILURE................7A2-68
DTC P1863 (FLASH CODE 28) HIGH CLUTCH PRESSURE SWITCH FAILURE..........7A2-72
DTC P0731 (FLASH CODE 41) 1st GEAR RATIO ERROR................................................7A2-76
DTC P0732 (FLASH CODE 42) 2nd GEAR RATIO ERROR...............................................7A2-76
DTC P0733 (FLASH CODE 43) 3rd GEAR RATIO ERROR................................................7A2-76
DTC P0734 (FLASH CODE 44) 4th GEAR RATIO ERROR................................................7A2-76
DTC P1750 (FLASH CODE 51) LOW & REVERSE BRAKE FAIL-SAFE
VALVE FAILURE........................................................................................................................7A2-78
DTC P1755 (FLASH CODE 52) 2-4 BRAKE FAIL-SAFE VALVE FAILURE....................7A2-80
DTC P0602 Programming Error ................................................................................... 7A2-82
SYMPTOM DIAGNOSIS.............................................................................................................7A2-83
SYMPTOM DIAGNOSIS TABLE...............................................................................................7A2-84
No. A1: VEHICLE DOES NOT RUN IN D, 3, 2, L and RANGE..........................................7A2-93
No. A2: VEHICLE DOES NOT RUN IN R RANGE................................................................7A2-94
No. A3: VEHICLE DOES NOT RUN IN D, 3, 2 and RANGE...............................................7A2-95
No. B1: VEHICLE RUNS IN N RANGE...................................................................................7A2-96
No. B2: POOR ACCELERATION AT STARTING.................................................................7A2-97
No. B3: ENGINE RACE UP DURING STARTING (SLIP)....................................................7A2-100
No. B4: LARGE SHOCK WHEN SHIFT LEVER IS CHANGED TO N TO D
RANGE OR N TO R RANGE....................................................................................................7A2-103
No. B5: ENGINE STALLS WHEN SELECTING FROM N RANGE TO R, D, 3, 2
OR L RANGE...............................................................................................................................7A2-104
No. B6: ENGINE STARTER DOES NOT RUN IN P OR N RANGE...................................7A2-106
No. B7: ENGINE STARTER RUNS EXCEPT IN P OR N RANGE.....................................7A2-106
No. B8: EXTENDED TIME LAG WHEN SHIFT LEVER IS CHANGED TO N TO D........7A2-106
No. B9: EXTENDED TIME LAG WHEN SHIFT LEVER IS CHANGED TO N TO R........7A2-106
No. B10: BRAKE IS APPLIED IN R RANGE..........................................................................7A2-107
No. B11: INSUFFICIENT STARTING OR SHAKING IN D RANGE...................................7A2-107

DIAGNOSIS (JR405E) 7A2-5
PAGE
NO. Z3: MODE LAMP (POWER DRIVE OR 3RD START) LIGHTS UP WHEN
THE POWER MODE OR 3RD START MODE IS TURNED OFF .................................. 7A2-137
NO. Z4: OIL TEMPERATURE WARNING LAMP LIGHTS UP ...................................... 7A2-137
NO. Z5: SELECT LEVER FEELING IS FAULTY. .......................................................... 7A2-137
NO. Z6: POOR FUEL CONSUMPTION ......................................................................... 7A2-138
NO. Z7: PATTERN SELECT SWITCH IS FAULTY........................................................ 7A2-138
NO. Z8: OIL IS SPLASHED DURING THE RUNNING .................................................. 7A2-138
NO. Z9: ABNORMAL SMELL ........................................................................................ 7A2-138
NO. Z10: ATF QUANTITY IS LOW OR HIGH ................................................................ 7A2-138
NO. Z11: ABNORMAL OIL PRESSURE........................................................................ 7A2-139
NO. Z12: REVERSE BUZZER DOES NOT RING .......................................................... 7A2-139
STALL TEST .................................................................................................................. 7A2-140
LINE PRESSURE TEST................................................................................................. 7A2-141
TIME LAG TEST............................................................................................................. 7A2-143
TEST DRIVE................................................................................................................... 7A2-144
SHIFT POINT CHART .................................................................................................... 7A2-147
SHIFT POINT DIAGRAM................................................................................................ 7A2-149
TCM VOLTAGE CHECK ................................................................................................ 7A2-154