Isuzu KB P190. Manual - part 1091

7A2-80   TRANSMISSION CONTROL SYSTEM (JR405E)

9

1.

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

2.

Inspect the 2-4 brake solenoid valve and
transmission fluid pressure (TFP) switch for
the following conditions:

• Physical damage

• Loose or improper installation 

3.

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

4.

Test the signal circuit between the 2-4 brake
TFP switch and the in-line harness connector
(pin 7 of E-54 male side) for the following
conditions:

• An open circuit

• A short to ground

• A short to the solenoid valve circuit

• High resistance 

5.

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

Did you find and correct the condition?

—

Go to Step 13

Go to Step 10

10

1.

Remove the 2-4 brake solenoid valve and TFP
switch from the valve body assembly and
perform function check. Refer to repair
instructions (On-Vehicle Service).

2.

Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 11

11

Repair or replace the valve body assembly. Refer
to repair instructions (On-Vehicle Service or Unit
Repair).

Did you complete the repair or 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.

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

Did the DTC fail this ignition?

—

Go to Step 2

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)   7A2-81

DTC P1860 (Flash Code 36)

Circuit Description

The torque converter clutch (TCC) solenoid valve
controls fluid acting on the lock up control spool valve,
which then controls lock up clutch 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 vehicle running conditions. The
solenoid valve provides a smooth engagement of the
torque converter clutch by operating on a duty cycle
percentage of ON time. The TCM monitors the TCC
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 TCC solenoid valve control circuit. 

Action Taken When the DTC Sets

• The TCM blinks the Check Trans lamp when the

diagnostic runs and fails.

• The TCM inhibits lock up control.

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.

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

Circuit/ System Testing DTC P1860

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.

Perform the Torque Converter Clutch (TCC)
Solenoid control with a scan tool.

3.

Command the solenoid valve ON and OFF.

Does the TCC solenoid valve click with each
command?

—

Go to Diagnostic 

Aids

Go to Step 3

3

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

4.

Turn ON the ignition, with the engine OFF. 

5.

Perform the TCC 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 8

Go to Step 4

4

Does the test lamp remain illuminated with each
command?

—

Go to Step 5

Go to Step 6

7A2-82   TRANSMISSION CONTROL SYSTEM (JR405E)

5

1.

Test the control circuit between the TCM (pin
17 of C-95) and the in-line harness connector
(pin 4 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
17 of C-95) and the in-line harness connector
(pin 4 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 17 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 4 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 TCC 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
TCC 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 TCC
solenoid valve and the in-line harness
connector (pin 4 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 12

Go to Step 10 

Step

Action

Value(s)

Yes

No

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-83

10

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

Did you complete the replacement?

—

Go to Step 12

—

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