Isuzu KB P190. Manual - part 1100

7A2-116   TRANSMISSION CONTROL SYSTEM (JR405E)

G2: Large Creeping Force 

G3: Small Creeping Force 

G4: Large Noise During Idle with Vehicle Stop

Transmission Range Switch & Selector Lever
Cable Checks

Inspect the transmission range switch and selector lever cable for
misadjusting or disordering. Refer to On-Vehicle Service section. 

Additional Checks 

Inspect the parking mechanism for faulty operation. 

Checks

Action

Checks

Action

Definition:
Vehicle accelerates in R, D, 3, 2 or L range, even though the accelerator pedal is not being stepped on. 

Diagnosis Hints

Too high idle speed is suspected. Inspect the engine for proper idle speed. 

Checks

Action

Definition:
Vehicle does not move, even though a run position is selected on a flat road during idling.

Diagnosis Hints

When the creep force is small in all positions, low engine output is suspected.
If the creep is normal only in the R position, operation of the fail-safe function
due to trouble in the electrical system is suspected.

Transmission Fluid Checks

Inspect the transmission fluid for the following conditions. If the transmission
fluid is extremely blacked, contaminated or smells burnt, slipping of clutch is
suspected. 

• Low quantity 

• Contamination 

• Smell 

Line Pressure Checks

Inspect the line pressure in forward ranges for a possible dropped pressure.
Refer to Line Pressure Test in Test Instruction section. 

Stall Speed Checks

Inspect the stall speed in forward ranges. Refer to Stall Test in Test
Instruction section. 

Control Valve Body Checks

Inspect the valve body for the following conditions.

• Faulty operation 

• Sticking spool valve

• Sticking shift solenoid valve. Perform function check. Refer to On-

Vehicle Service section. 

• Clogged hydraulic circuit

Torque Converter Checks

Inspect the torque converter for faulty operation.

Clutch and Brake Checks

Inspect the low clutch for slipping. 

Additional Checks 

• Inspect the engine for proper outputs. Refer to appropriate inspection

chart in engine section. 

• Inspect the TCM grounds for being clean, tight, and in their proper

locations.

• Inspect the ground return circuit for being clean, tight, and in their proper

locations.

Checks

Action

Definition:
Transmission is noisy during idle in all range.

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-117

H1: Judder Occurs at Lock Up 

H2: Large Shock at Lock Up 

H3: Lock Up Point is High or Low 

I1: No Lock Up 

Diagnosis Hints

• Causes such as the solenoid operating sound or a faulty oil pump are

suspected.

• Distinguishing 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 other than the transmission may be

generated around the engine, and should be checked carefully.

Notice:  When the noise is generated only at the time of a gear shift, it may
be the sound of transmission fluid flowing 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 components. If the sound varies
depending on the vehicle speed, it may be the gear noise of the output
system, or the gear noise of the input system or a faulty torque converter.

Checks

Action

Checks

Action

Definition:
Judder occurs when lock up area. 

Diagnosis Hints

Slip due to burning of the torque converter clutch (TCC) facing or insufficient
engagement due to dropped working pressure are suspected. Refer to
category No. “l1: No Lock Up “.

Notice: When the TCC facing has burnt, foreign material mixed in the oil
cooler is suspected. In such a case, inspect the oil cooler circuit for clogging
of the oil cooler.

Checks

Action

Definition:

• A large shock is felt at lock up.

• Lock up point is excessively high or low. 

Diagnosis Hints

Incorrect input signals or faulty operation of torque converter clutch (TCC) is
suspected. Refer to category No. “I1: No Lock Up”.

Checks

Action

Definition:
Lock up is not performed even though lock up control conditions being satisfied. 

Diagnosis Hints

• Monitor the signal to the torque converter clutch (TCC) solenoid valve

while carrying out a running test.

• When the transmission fluid temperature is lower than 20

°C (68°F),

lock up control is inhibited.

• When the output signal to the TCC solenoid valve is sent correctly,

causing no lock up, clogged hydraulic circuits or malfunction of the TCC
piston may be suspected.

• Even with the lock up area, the output signal to the TCC solenoid valve

is not sent, a fault of the transmission fluid temperature (TFT) sensor
controlling the lock up may be suspected. 

Notice: When the TCC facing has burnt, foreign material mixed in the oil
cooler is suspected. In such a case, inspect the oil cooler circuit for clogging
of the oil cooler. 

7A2-118   TRANSMISSION CONTROL SYSTEM (JR405E)

J1: Transmission Fluid Leaks from Breather 

J2: Transmission Fluid Leaks Between Engine and Converter Housing

J3: Transmission Fluid Leaks Between Converter Housing and Transmission Case

J4: Transmission Fluid Leaks Between Transmission Case and Extension Housing

J3: Transmission Fluid Leaks from Oil Pan

J3: Transmission Fluid Leaks from Manual Shaft Oil Seal 

J3: Transmission Fluid Leaks from Oil Cooler Pipe Joint

Z1: Transmission Overheat 

Transmission Fluid Checks

Inspect the transmission fluid for the following conditions. If the transmission
fluid is extremely blacked, contaminated or smells burnt, slipping of clutch is
suspected. 

• Low quantity 

• Contamination 

• Smell 

Control Valve Body Checks

Inspect the valve body for the following conditions.

• Faulty operation 

• Sticking spool valve

• Sticking TCC solenoid valve. Perform function check. Refer to On-

Vehicle Service section. 

• Clogged hydraulic circuit

Sensor Checks

Inspect the TFT sensor. Use the Temperature vs. Resistance table to test
the TFT sensor at various temperature levels to evaluate the possibility of a
skewed sensor.

Checks

Action

Checks

Action

Definition:
Transmission fluid leaks from breather.

Diagnosis Hints

Transmission fluid quantity is excessively high. 

Checks

Action

Definition:
Transmission fluid leaks between engine and converter housing.
Transmission fluid leaks between converter housing and transmission case.
Transmission fluid leaks between transmission case and extension housing.
Transmission fluid leaks from oil pan.
Transmission fluid leaks from manual shaft oil seal. 
Transmission fluid leaks from oil cooler pipe joint.

Diagnosis Hints

Faulty oil seal or contact surface is suspected. 

Checks

Action

Definition:
Smells burnt or smoke from transmission. 

Diagnosis Hints

• Transmission fluid quantity is excessively high. 

• Slipping of the clutch is suspected. Gear ratio error DTC might be set.

• Clogged oil cooler. 

• Faulty operation of oil pump. 

• Faulty torque converter clutch (TCC) piston. 

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-119

Z2: Mode Lamp (Power Drive or 3rd Start) Does Not Turn On 

Z3: Mode Lamp (Power Drive or 3rd Start) Does Not Turn Off 

Z4: A/T Oil Temperature Lamp Turns On

Z5: Selector Lever Feeling is Faulty 

Z6: Poor Fuel Consumption 

Checks

Action

Definition:
Mode lamp on the instrument panel (IP) cluster does not turn ON even though the switch is ON. 

Diagnosis Hints

• Faulty mode switch circuit. 

• Faulty mode switch. 

• Faulty lamp control circuit. 

• Faulty IP cluster. 

Checks

Action

Definition:
Mode lamp on the instrument panel cluster does not turn OFF even though the switch is OFF. 

Diagnosis Hints

• Faulty mode switch circuit. 

• Faulty mode switch. 

• Faulty lamp control circuit. 

• Faulty IP cluster. 

Checks

Action

Definition:
A/T oil temperature lamp turns On sometimes. 

Diagnosis Hints

• 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. 

• When the vehicle is stuck in the mud or continues to accelerate under

overload, transmission fluid temperature increases and lamp may be
turned On. 

• If the lamp is On under usual conditions, following causes are suspected. 

- Transmission fluid level has increased for some fault. Refer to category

No. “Z1: Transmission Overheat”.

- Skewed transmission fluid temperature (TFT) sensor. 

Checks

Action

Definition:
Selector lever feeling is faulty.   

Diagnosis Hints

• Inspect the selector lever cable for misadjusting or disordering.

• Faulty manual plate. 

Checks

Action

Definition:
Poor fuel consumption. 

Diagnosis Hints

The same causes as in category No. “C1 - C8: Engine Race Up (Slipping)” are
suspected.