engine ISUZU TF SERIES 2004 Workshop Manual
Page 4112 of 4264
7A2-120 DIAGNOSIS (JR405E)
No. D2: Gear is Shifted Frequently
Description:
Gear is shifted down immediately though the accelerator pedal is stepped on a little in D, 3, 2, or L range.
Diagnosis Hints:
Basically, the same cause as "No. D1: Faulty gear shifting" is considered. However, as possible cause, fault
input signal of throttle position sensor or speed sensor, fault input signal of inhibitor switch, or fault of TCM
power source, earth, ground return wire are considered first.
Then, slip of the clutch, fault of the control valve are considered.
No. D3: Gear Shift Point is Low or High at All Point
No. D4: Gear Shift Point is Low or High at Limited Point
Description:
Gear shift point is deviated from the shift diagram.
Gear is not shifted up properly though the vehicle is accelerated.
Gear is not shifted immediately and enough acceleration cannot be obtained though the accelerator pedal is
stepped on.
Diagnosis Hints:
If the cause is not faulty gear shift, throttle position sensor disordered or fault input of speed sensor is
considered. Output signal of the throttle position sensor is changed to linear one.
(Refer the paragraph about the faulty throttle position sensor of "No. D1: Faulty gear shifting".)
No. D5: No Kick-down
Description:
The engine speeds up but vehicle speed does not increase when the accelerator pedal is stepped on at the
starting.
Diagnosis Hints:
When the gear shift is normal only without kick-down, possibility of fault of the throttle position sensor. Check
that the throttle voltage increases linearly in proportion to the throttle opening.
(Refer the paragraph about the faulty throttle position sensor of "No. D1: Faulty gear shifting".)
Page 4119 of 4264
DIAGNOSIS (JR405E) 7A2-127
No. F1: Low Maximum Speed or Poor Acceleration
Description:
Starting acceleration is poor.
Acceleration is slow though the accelerator pedal is stepped on during the running.
Diagnosis Hints:
In addition to the low engine output, faulty gear shifting of AT or fixing at the 3rd position may be possible.
Therefore, in case of such a trouble that "maximum speed is low, and acceleration is poor", it should be cleared
up whether the trouble is originated from the engine system of AT system by a running test, inspection of stall
revolution, etc.
Possible Cause:
Clogged air cleaner, out of injection timing, dropped compression pressure, etc.
Fixing at 3rd position (fail-safe activated).
Since the gear is fixed at the 3rd position because of the fail-safe function, a trouble that "Maximum
speed is low, and acceleration is poor" is resulted. In this case, the DTC is memorized.
When TCM stops operation because of faulty TCM ground, the gear is fixed at the 3rd position because
of a mechanical reason. In this case, no DTC is memorized.
Disordered inhibitor switch .
Incorrect properties of throttle opening signal (serial communication) of throttle position sensor.
Throttle opening signal (serial communication) of the throttle position sensor does not change in
proportion to the throttle opening. In this case, fixing at the high or low gear results in such a trouble
that "Maximum Speed is Low and Acceleration is Poor".
Slip of clutch (low clutch, high clutch).
If slip of clutch is caused, a DTC (gear ratio error) is stored.
Dropped line pressure.
Trouble in the torque converter system (faulty operation).
Step Action Yes No
1 Test Drive.
Is the gear smoothly shifted in the order of 1st to 2nd, 2nd to 3rd,
3rd to 4th gear and lock up?
Clogged air
cleaner, out of
injection timing,
dropped
compression
pressure, etc. Go to Step 2
2 Gear ratio trouble diagnosis.
Travel in the following sequence for about 7 seconds or more in
each range: Start in the L range (1st) to 2 range (2nd) to 3 range
(3rd) to D range (4th) (to detect the gear ratio trouble exactly, this
process should be carried out)
Go to Step 3 Go to Step 3
3 Are any DTCs stored?
Go to DTC Chart Go to Step 4
Page 4122 of 4264
7A2-130 DIAGNOSIS (JR405E)
No. F2: Engine Races Up During Acceleration (Slip)
Description:
The engine speed up when the accelerator pedal is stepped on for acceleration and the gear is shifted up or
down.
Only the engine speeds up but vehicle speed does not increase when the accelerator pedal is stepped on for
acceleration during the running.
Diagnosis Hints:
Basically same causes as "No. C1 - C8: Engine races up (slip) by shift up or shift down" are considered.
When the condition of No. C1-C8 grows worse, symptom of No. F2 results.
No. F3: Noise or Vibration During the Running in R, D, 3, 2 or L Range
Description:
Noise or vibration is generated in the vicinity of AT during the running.
Diagnosis Hints:
Cause other than AT can be also considered. It is effective means to reproduce a running condition using a lift
up, chassis dynamo, etc. to investigate the origin (generating condition) of noise and vibration.
Caution:
Lifting up some unit to test it accompanies danger. Provide safety measures as far as possible and
carry out the test with sufficient care.
Possible Cause:
Following sources of noise or vibration other than the AT can be considered.
Noise from differential gears.
Noise from propeller shaft.
The bearing support in the middle of the propeller shaft has fatigued, and the bend angle of the propeller shaft
has changed, causing vibration at the time of start.
Unbalanced and poor uniformity of tires cause vibration.
No. F4: Engine Brake Does Not Apply in L Range
Description:
The engine brake does not apply, allowing the vehicle to run freely when the accelerator pedal is released at low
speed in L range.
Possible Cause:
Slip of clutch (low & reverse brake)
If slip of clutch is caused, a DTC (gear ratio error) is stored.
Faulty input/output signal system.
Low & reverse brake duty solenoid
Faulty control valve (faulty operation, sticking).
Page 4123 of 4264
DIAGNOSIS (JR405E) 7A2-131
No. F5: Engine Stalls Before Vehicle Stops from Running
Description:
The engine stalls simultaneously with the vehicle stop when the brake pedal is stepped on to stop the vehicle
during the running.
Possible Cause:
Trouble on the engine system side (fuel injection control, engine speed control, etc.) is considered.
Refer to "No. B5: Engine stalls when selecting from N range to R, D, 3, 2 or L range".
No. G1: Vehicle Moves in P Range or Parking Gear is Not
Disengaged other than P Range
Description:
Vehicle moves though it stops at a slope and P range is selected.
The engine stalls and vehicle does not move though other than P range is selected and the accelerator pedal is
stepped on.
Possible Cause:
Trouble of the parking mechanism (noise or shock may result).
Disordered selector cable (only when traveling in the P range).
If the vehicle moves in the N range, follow the procedure of "No. B1: Vehicle runs in N range".
No. G2: Creep Force is Large
Description:
Vehicle accelerates in D, 3, 2, L, and R ranges though the accelerator pedal is not stepped on.
Possible Cause:
Too high engine idling speed (not attributable to AT).
Page 4124 of 4264
7A2-132 DIAGNOSIS (JR405E)
No. G3: Creep Force is small
Description:
Vehicle does not move though a run range is selected on a flat road during the idling.
Diagnosis Hints:
When the creep force is small in all ranges, low engine output is considered. Another possible cause is slip of
clutch. If the creep is normal only in the R range, operation of the fail-safe function due to a trouble in the electrical
system is considered.
Possible Cause:
Slip of clutch (low clutch).
If slip of clutch is caused, a DTC (gear ratio error) is stored.
Low engine output (low idling speed, out of injection timing, lowered compression pressure, etc.).
Shortage or faulty quality of ATF.
Disconnection or short circuit of solenoid valve output.
Clogged oil passage of solenoid valve output.
Faulty ground return line in AT assembly.
If the ground return line earth is faulty, clutch pressure may decrease causing slip of the clutch.
Trouble in the torque converter system (faulty operation).
Step Action Yes No
1 Gear ratio trouble diagnosis.
Travel in the following sequence for about 7 seconds or
more in each range: Start in the L range (1st) to 2 range
(2nd) to 3 range (3rd) to D range (4th) (to detect the gear
ratio trouble exactly, this process should be carried out)
Go to Step 2 Go to Step 2
2 Are any DTCs stored?
Go to DTC Chart Go to Step 3
3 Are the quantity, contamination and smell normal? If the ATF level is low,
replenish up to the
specified level.
Go to Step 4
If ATF is extremely
black and
contaminated and
smells burnt, slip of the
clutch is supposed.
Overhaul the AT unit.
4 Are the idling speed and other engine system normal?
Go to Step 5
Repair the defect or
replace.
5 Is the stall revolution normal in D, 3, 2 and L range? Refer
the STALL TEST section in this manual.
Go to Step 6
Repair the defect or
replace.
6 Is the line pressure normal? Refer the LINE PRESSURE
TEST section in this manual. Trouble in the AT
assembly or control
valve.
Repair the defect or
replace.
Page 4125 of 4264
DIAGNOSIS (JR405E) 7A2-133
No. G4: Large Noise During Idling with the Vehicle in Stop State
Description:
The transmission is noisy during the idling speed in all ranges.
Diagnosis Hints:
Causes such as solenoid operating sound or faulty oil pump are considered.
Distinguishing to some extent is possible by stopping the solenoid operation temporarily, checking the correlation
for the former case and, changing the line pressure and confirming the correlation with noise.
As a matter of course, noise may be generated around the engine, for instance, other than the AT and should be
checked carefully.
Note:
When the noise is generated only at the time of gear shift, it may be the sound of flowing ATF or gear
noise. If the sound varies depending on the gear speed to be shifted, it may be the gear noise generated
from the planetary gear and its related components. If the sound varies depending on the vehicle
speed, it may be the gear noise of the output system, and if varying depending on the engine speed, it
may be the gear noise of the input system or faulty torque converter.
In either case, sound may be "noise" depending on the origin and resonance object. When the object
generating the sound (resonance object) and the sound source (vibration source) are different,
investigation of the cause may be difficult.
No. H1: Judder Occurs at the Lock-up
Diagnosis Hints:
The vehicle body judders at lock-up.
Diagnosis Hints:
Slip due to burning of the lockup piston or insufficient fastening due to dropped working pressure are considered.
Trouble diagnosis flow is basically the same as "No. I1: No lock-up".
Note:
When the lock-up piston has burnt, foreign material mixed in the oil cooler is considered. In such a
case, inspect the oil cooler circuit for clogging of the oil cooler.
No. H2: Large Lock-up Shock
No. H3: Lock-up Point is High or Low
Description:
Large shock is felt at lock-up.
Lock-up point is excessive high or low.
Diagnosis Hints:
Out of properties of input sensor or faulty lock-up piston pressure system are considered.
Trouble diagnosis flow is basically the same as "No. I1: No lock-up".
Page 4128 of 4264
7A2-136 DIAGNOSIS (JR405E)
No. J1: Oil Leaks from Breather
Description:
Oil leaks from breather.
Possible Cause:
ATF quantity is excessively.
No. J2: Oil Leaks Between Engine and Converter Housing
No. J3: Oil Leaks Between Main Case and Converter Housing
No. J4: Oil Leaks Between Main Case and Rear Housing
No. J5: Oil Leaks from Oil Pan
No. J6: Oil Leaks from Manual Shaft Oil Seal
No. J7: Oil Leaks from Oil Cooler Pipe Joint
Description:
Oil leaks between engine and converter housing.
Oil leaks between converter housing and main case.
Oil leaks between main case and rear housing.
Oil leaks from oil pan.
Oil leaks from manual shaft oil seal.
Oil leaks from oil cooler pipe joint.
Possible Cause:
Faulty oil seal or sealing of contact surface is considered.
No. Z1: Transmission Overheat
Description:
You smell the transmission burning.
The transmission smokes.
Possible Cause:
Slip of clutch.
If slip of clutch is caused, a DTC (gear ratio error) is stored.
Clogged oil cooler (foreign substance mixed)
ATF stirred excessively (too much ATF).
Faulty torque converter operating pressure.
Faulty lock-up piston.
Page 4130 of 4264
7A2-138 DIAGNOSIS (JR405E)
No. Z6: Poor Fuel Consumption
Description:
Poor fuel consumption.
Diagnosis Hints:
Basically same causes as "No. C1 - C8: Engine races up (slip) by shift up or shift down" are considered.
No. Z7: Pattern Select Switch is Faulty
Description:
Shift pattern does not change though the pattern select switch is turned on.
Possible Cause:
Faulty mode select switch is considered.
No. Z8: Oil is Splashed During the Running
Description:
Oil is splashed during the running
Possible Cause:
ATF quantity is too high.
No. Z9: Abnormal Smell
Description:
Abnormal smell.
Diagnosis Hints:
Basically a trouble in the AT main unit.
No. Z10: ATF Quantity is Low or High
Description:
Oil quantity is low or high.
Possible Cause:
In case of oil level is high.
ATF temperature is low when ATF quantity is checked.
In case of oil level is low.
ATF leaks is considered. Check the AT main unit and cooler circuit.
Page 4131 of 4264
DIAGNOSIS (JR405E) 7A2-139
No. Z11: Abnormal Oil Pressure
Description:
Oil pressure is low or high.
Possible Cause:
Basically, the same cause as "No. C1 - C8: Engine races up (slip) by shift up or shift down" is considered.
In case of oil pressure is low, faulty oil pump is considered.
No. Z12: Reverse Buzzer Does Not Ring
Description:
Reverse buzzer does not ring in R range.
Possible Cause:
Disordered select cable.
Disordered select lever.
Disordered inhibitor switch.
Page 4132 of 4264
7A2-140 DIAGNOSIS (JR405E)
STALL TEST
CAUTION:
Because A/T may break down, do not perform the stall test continuously.
Procedure
1. Chock the four wheels.
2. Warm up the engine.
3. Apply the parking brake.
4. Step on the foot brake fully.
5. Set the select lever to either D, 3, 2, L or R range.
6. Step on the accelerator pedal fully.
7. When the engine speed becomes constant, record tha
t
value quickly.
Stall Speed
Standard: 2600±150 rpm
Evaluation
1. If the stall speed is higher than standard value in all
ranges.
Low line pressure.
Abraded oil pump.
Faulty operation of low clutch.
Adjustment error of or faulty inhibitor switch.
ATF leaking from oil pump, control valve, or
transmission case.
Fixed pressure regulator valve and pilot valve.
2. If the stall speed is higher than standard value in D, 3, 2
and L ranges.
Slip of low clutch.
Slip of low one-way clutch.
3. If the stall speed is higher than standard value in
R
range.
Slip of low & reverse brake.
Slip of reverse clutch.
4. If the stall speed is lower than standard value in all
ranges.
Slip of one-way clutch (in torque converter).
Faulty engine.