Isuzu KB P190. Manual - part 1085

7A2-56   TRANSMISSION CONTROL SYSTEM (JR405E)

5

1.

Test the control circuit between the TCM (pin
23 of C-95) and the in-line harness connector
(pin 6 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 12

Go to Step 11

6

1.

Test the control circuit between the TCM (pin
23 of C-95) and the in-line harness connector
(pin 6 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 12

Go to Step 7

7

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 23 of C-95). 

4.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 12

Go to Step 11

8

1.

Inspect for an intermittent and for a poor
connection at the in-line harness connector
(pin 6 of E-54).

2.

Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 12

Go to Step 9

9

1.

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

2.

Inspect the PC 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 in-line harness connector.

4.

Test the control circuit between the PC
solenoid valve and the in-line harness
connector (pin 6 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 

5.

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

Did you find and correct the condition?

—

Go to Step 12

Go to Step 10 

10

Replace the PC solenoid valve. Refer to repair
instructions (On-Vehicle Service). 

Did you complete the replacement?

—

Go to Step 12

—

Step

Action

Value(s)

Yes

No

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-57

11

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

Did you complete the replacement?

—

Go to Step 12

—

12

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.

Drive the vehicle while observing the DTC
Information with a scan tool. 

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 13

13

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

7A2-58   TRANSMISSION CONTROL SYSTEM (JR405E)

DTC P0753 (Flash Code 31)

Circuit Description

The low & reverse brake solenoid valve controls fluid
acting on spool valves in the low & reverse brake
hydraulic circuits, which then controls low & reverse
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 low & reverse 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 low & reverse 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 low & reverse 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 P0753

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 Low & Reverse Brake Solenoid
control with a scan tool.

4.

Command the solenoid valve ON and OFF.

Does the low & reverse brake solenoid valve click
with each command?

—

Go to Diagnostic 

Aids

Go to Step 4

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-59

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 5 of E-54 female side) and a known
good ground. 

4.

Turn ON the ignition, with the engine OFF. 

5.

Perform the Low & Reverse 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 6
of C-95) and the in-line harness connector (pin
5 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 6
of C-95) and the in-line harness connector (pin
5 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 6 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 5 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