Isuzu KB P190. Manual - part 1086

7A2-60   TRANSMISSION CONTROL SYSTEM (JR405E)

10

1.

Remove the transmission oil pan. Refer to
repair instructions (On-Vehicle Service). 

2.

Inspect the low & reverse brake solenoid valve
for the following conditions:

• Physical damage of solenoid valve 

• Loose or improper installation of solenoid

valve

3.

Inspect for an intermittent and for a poor
connection at the harness connector of the
low & reverse brake solenoid valve or in-line
harness connector. 

4.

Inspect for an intermittent and for a poor
connection of ground wire. 

5.

Test the control circuit between the low &
reverse brake solenoid valve and the in-line
harness connector (pin 5 of E-54 male side)
for the following conditions:

• An open circuit

• A short to ground

• A short to the other solenoid valve circuit

• High resistance 

6.

Repair the connection(s) or circuit(s) as
necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 11

11

Replace the low & reverse brake solenoid valve.
Refer to repair instructions (On-Vehicle Service). 

Did you complete the replacement?

—

Go to Step 13

—

12

Important: Replacement TCM must be
programmed.
Replace the TCM. Refer to TCM Replacement.

Did you complete the replacement?

—

Go to Step 13

—

13

1.

Reconnect all previously disconnected
components or harness connector(s).

2.

Clear the DTCs with a scan tool.

3.

Turn OFF the ignition for 30 seconds. 

4.

Start the engine.

5.

Lift the driving wheels or drive the vehicle
while observing the DTC Information with a
scan tool. 

Did the DTC fail this ignition?

—

Go to Step 4

Go to Step 14

14

Observe the DTC Information with a scan tool.

Are there any DTCs that you have not diagnosed?

—

Go to DTC List 

System OK

Step

Action

Value(s)

Yes

No

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-61

DTC P0758 (Flash Code 32)

Circuit Description

The 2-4 brake solenoid valve controls fluid acting on
spool valves in the 2-4 brake hydraulic circuits, which
then controls 2-4 brake apply and release. The
solenoid valve is installed to the lower part of the valve
body assembly. The TCM controls the solenoid valve
by a duty cycle (pulse width modulation [PWM]) signal
based on the commanded gear position. The solenoid
valve provides a smooth gearshift by operating on a
duty cycle percentage of ON time. The TCM monitors
the 2-4 brake solenoid valve operating status through
the feedback circuit. If the TCM detects an improper
voltage level on the control circuit, this DTC will set. 

Condition for Running the DTC

• The ignition switch is ON.

Condition for Setting the DTC

• The TCM detects an open circuit or short circuit on

the 2-4 brake solenoid valve control circuit.

 Action Taken When the DTC Sets

• The TCM blinks the Check Trans lamp when the

diagnostic runs and fails.

During the vehicle running;

• The TCM holds the last gear position when the

diagnostic runs and fails.

• The TCM stops 2-4 brake solenoid valve. 

• The TCM inhibits lock up control.

After the vehicle stopped;

• The TCM stops all shift solenoid valves and fixes

to the 3rd gear. If a fail-safe valve problem is
detected, the shift solenoid valves are not stopped
but gear is fixed to the 3rd gear.

• The TCM stops PC solenoid valve. 

Condition for Clearing the DTC

• The TCM turns OFF the Check Trans lamp when

the diagnostic runs and does not fail at next
ignition cycle.

• A current DTC clears when the diagnostic runs and

does not fail at next ignition cycle.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

• Use the Clutch, Brake, Solenoid and Pressure

Switch Logic table to verify each component works
properly within the selected gear range.

Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or TCM Connector End
Views

Circuit/ System Testing DTC P0758

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check -
Transmission Controls?

—

Go to Step 2

Go to Diagnostic 

System Check -

Transmission 

Controls

2

1.

Install a scan tool. 

2.

Turn OFF the ignition for 30 seconds. 

3.

Lift the driving wheels or drive the vehicle
while observing the DTC Information with a
scan tool.

Is DTC P1875 also set?

—

Go to DTC P1875

Go to Step 3

3

1.

Park the vehicle.

2.

Turn ON the ignition, with the engine OFF.

3.

Perform the 2-4 Brake Solenoid control with a
scan tool.

4.

Command the solenoid valve ON and OFF.

Does the 2-4 brake solenoid valve click with each
command?

—

Go to Diagnostic 

Aids

Go to Step 4

7A2-62   TRANSMISSION CONTROL SYSTEM (JR405E)

4

1.

Turn OFF the ignition. 

2.

Disconnect the in-line harness connector (E-
54) near the transmission range switch.

3.

Connect a test lamp between the control
circuit (pin 9 of E-54 female side) and a known
good ground. 

4.

Turn ON the ignition, with the engine OFF.

5.

Perform the 2-4 Brake Solenoid control with a
scan tool.

6.

Command the solenoid valve ON and OFF.

Does the test lamp turn ON and OFF with each
command?

—

Go to Step 9

Go to Step 5

5

Does the test lamp remain illuminated with each
command?

—

Go to Step 6

Go to Step 7

6

1.

Test the control circuit between the TCM (pin 7
of C-95) and the in-line harness connector (pin
9 of E-54 female side) for a short to battery or
ignition voltage. 

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

7

1.

Test the control circuit between the TCM (pin 7
of C-95) and the in-line harness connector (pin
9 of E-54 female side) for the following
conditions:

• An open circuit

• A short to ground

• High resistance 

2.

Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 8

8

1.

Turn OFF the ignition. 

2.

Disconnect the TCM harness connector.

3.

Inspect for an intermittent and for a poor
connection at the harness connector of the
TCM (pin 7 of C-95). 

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

9

1.

Inspect for an intermittent and for a poor
connection at the in-line harness connector
(pin 9 of E-54).

2.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 10

Step

Action

Value(s)

Yes

No

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-63

10

1.

Remove the transmission oil pan. Refer to
repair instructions (On-Vehicle Service). 

2.

Inspect the 2-4 brake solenoid valve for the
following conditions:

• Physical damage of solenoid valve 

• Loose or improper installation of solenoid

valve

3.

Inspect for an intermittent and for a poor
connection at the harness connector of the 2-
4 brake solenoid valve or in-line harness
connector.

4.

Inspect for an intermittent and for a poor
connection of ground wire. 

5.

Test the control circuit between the 2-4 brake
solenoid valve and the in-line harness
connector (pin 9 of E-54 male side) for the
following conditions:

• An open circuit

• A short to ground

• A short to the other solenoid valve circuit

• High resistance 

6.

Repair the connection(s) or circuit(s) as
necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 11

11

Replace the 2-4 brake solenoid valve. Refer to
repair instructions (On-Vehicle Service). 

Did you complete the replacement?

—

Go to Step 13

—

12

Important: Replacement TCM must be
programmed.
Replace the TCM. Refer to TCM Replacement.

Did you complete the replacement?

—

Go to Step 13

—

13

1.

Reconnect all previously disconnected
components or harness connector(s).

2.

Clear the DTCs with a scan tool.

3.

Turn OFF the ignition for 30 seconds. 

4.

Start the engine.

5.

Lift the driving wheels or drive the vehicle
while observing the DTC Information with a
scan tool. 

Did the DTC fail this ignition?

—

Go to Step 4

Go to Step 14

14

Observe the DTC Information with a scan tool.

Are there any DTCs that you have not diagnosed?

—

Go to DTC List 

System OK

Step

Action

Value(s)

Yes

No