Isuzu KB P190. Manual - part 1099

7A2-112   TRANSMISSION CONTROL SYSTEM (JR405E)

D3: Gearshift Point is Low or High at All Points

D4: Gearshift Point is Low or High at Limited Area 

D5: No Kick-down 

E1: No Gearshift 

Checks

Action

Definition:

• Gearshift point is deviated from the shift speed chart. 

• Gear is not shifted up properly, even though the vehicle is accelerating.

• Gear is not shifted immediately and enough acceleration cannot be obtained, even though the accelerator pedal is being

stepped on.

Diagnosis Hints

• Inspect the output shaft speed (OSS) sensor for faulty operation. 

• Incorrect accelerator pedal position signal is suspected. Observe the

Accelerator Pedal Position (APP). APP parameter should change linearly
from 0 to 99 or 100% according to the accelerator pedal operation.

Checks

Action

Definition:
The engine speeds up but the vehicle speed does not increase when the accelerator pedal is being stepped on at starting.

Diagnosis 

Hints

Incorrect accelerator pedal position signal is suspected. Observe the
Accelerator Pedal Position (APP). APP parameter should change linearly from
0 to 99 or 100% according to the accelerator pedal operation.

Checks

Action

Definition:

• Gear is fixed, such as no gearshift from 1st to 2nd, 2nd to 3rd, and 3rd to 4th.

• Sometimes the gear is shifted, and sometimes it is not possible. 

Diagnosis Hints

• Fixing at same gear speed, a signal error from the accelerator pedal

position (APP) sensor or trouble in the transmission main unit are
suspected.

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

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. 

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

Clutch and Brake Checks

Inspect the low clutch, high clutch or low & reverse brake for slipping. 

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-113

E2: Only 4th Gear is Not Selectable 

E3: Gear is Changed from 2nd to 3rd in 2 Range 

E4: Gear is Changed from 1st to 2nd in L Range 

E5: Gear is Changed from 3rd to 4th in 3 Range 

Sensor Checks

Inspect the input shaft speed (ISS) sensor and output shaft speed (OSS)
sensor for faulty operation. 

Additional Checks 

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

locations.

• Observe the Accelerator Pedal Position (APP). APP parameter should

change linearly from 0 to 99 or 100% according to the accelerator pedal
operation.

Checks

Action

Checks

Action

Definition:
Gearshift is not possible from 3rd to 4th even though the vehicle is accelerating. 

Diagnosis Hints

When the transmission fluid temperature is lower than 10

°C (50°F), gearshift

from the 3rd to the 4th is inhibited.

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. 

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

Clutch and Brake Checks

Inspect the low clutch for seizing. 

Sensor Checks

Inspect the transmission fluid temperature (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

Definition:

• Gear is shifted from 2nd to 3rd in 2 range.

• Gear is shifted from 1st to 2nd in L range.

• Gear is shifted from 3rd to 4th in 3 range.

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. 

7A2-114   TRANSMISSION CONTROL SYSTEM (JR405E)

F1: Low Maximum Speed or Poor Acceleration 

F2: Engine Race Up (Slipping) During Acceleration 

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

Checks

Action

Checks

Action

Definition:

• Starting acceleration is poor.

• Acceleration is slow, even though the accelerator pedal is stepped on during the running.

Diagnosis Hints

In addition to the low engine output, faulty gearshift of the transmission or
fixing at the 3rd gear in the fail-safe operation may also be possible.
Therefore, if “maximum speed is low, and acceleration is poor”, it should be
cleared up whether the trouble originates from the engine system or
transmission control system by a running test, inspection of stall speed, etc.

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. 

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 and high 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.

• Observe the Accelerator Pedal Position (APP). APP parameter should

change linearly from 0 to 99 or 100% according to the accelerator pedal
operation.

Checks

Action

Definition:

• Engine speed increases but the vehicle speed does not increase when the accelerator pedal is being stepped on. 

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-115

F3: Noise or Vibration Occurs During in R, D, 3, 2 or L Range

F4: Engine Brake Does Not Apply in L Range 

F5: Engine Stalls Before Vehicle Stops from Running

G1: Vehicle Moves in P Range or Parking is Not Disengaged in Other Than P Range

Diagnosis Hints

The same causes as in category No. “C1 - C8: Engine Race Up (Slipping)”
are suspected. When the condition of No. C1 - C8 grows worse, No. F2
results.

Checks

Action

Definition:
Noise or vibration occurs in the vicinity of the transmission during running. 

Diagnosis 

Hints

Cause other than transmission is suspected. Reproduce the running
condition using a lift up, chassis dynamo, etc. to investigate the origin of the
noise and vibration.

Additional Checks 

• Inspect the differential gear noise. 

• Inspect the propeller shaft noise. 

• Inspect the tires for unbalanced or poor uniformity. 

Checks

Action

Checks

Action

Definition:
The engine brake does not apply, allowing the vehicle to run freely when the accelerator pedal is released at low speed in L
range.

Diagnosis Hints

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

Line Pressure Checks

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

Clutch and Brake Checks

Inspect the low & reverse brake for slipping. 

Sensor Checks

Inspect the input shaft speed (ISS) sensor and output shaft speed (OSS)
sensor for faulty operation. 

Checks

Action

Definition:
The engine stalls simultaneously with the vehicle when the brake pedal is stepped on to stop the vehicle during running.

Diagnosis Hints

The same causes as in category No. “B5: Engine Stalls When Selector Lever
is Changed from N to R, D, 3, 2 or L Range” is suspected. 

Checks

Action

Definition:
Vehicle moves even though it stops on a slope and P range is selected.
Vehicle does not move even though a position other than P range is selected, and the accelerator pedal is being stepped on.

Diagnosis Hints

If the vehicle moves in N range, refer to category No. “B1: Vehicle Runs in
N Range”.