Isuzu N-Series. Manual - part 907

Transmission Control System (Smoother) 7A-83

1. Test the signal circuit between the TCM (pin 5

of B-427 connector) and the input shaft speed
sensor harness connector (pin 2 of J-139
connector) for the following conditions:

• An open circuit
• A short to ground
• A short to the low reference
• High resistance

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 18

Go to Step 14

1. Test the low reference circuit between the

TCM (pin 11 of B-427 connector) and the input
shaft speed sensor harness connector (pin 1
of J-139 connector) for an open circuit or high
resistance.

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 18

Go to Step 14

1. Turn OFF the ignition.
2. Inspect for an intermittent and for poor

connections at the harness connector of the
input shaft speed sensor (pins 1 and 2 of J-139
connector).

3. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 18

Go to Step 15

1. Turn OFF the ignition.
2. Disconnect the TCM harness connector.
3. Inspect for an intermittent and for poor

connections on the input shaft speed sensor
circuits at the harness connector of the TCM
(pins 5 and 11 of B-427 connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 18

Go to Step 17

1. Remove the input shaft speed sensor. Refer to

Input Shaft Speed Sensor Replacement in this
section.

2. Visually inspect the input shaft speed sensor

for the following conditions:

• Physical damage
• Loose or improper installation

3. The following conditions may cause this DTC

to set:

• Excessive air gap between the input shaft

speed sensor and the counter shaft

• Electromagnetic interference in the input

shaft speed sensor circuits

• Foreign material passing between the

input shaft speed sensor and the counter
shaft

Did you find and correct the condition?

—

Go to Step 18

Go to Step 16

Replace the input shaft speed sensor. Refer to Input
Shaft Speed Sensor Replacement in this section.

Did you complete the replacement?

—

Go to Step 18

—

Step

Action

Value(s)

Yes

7A-84 Transmission Control System (Smoother)

Important:
Replacement TCM must be programmed and
learned.
Replace the TCM. Refer to Transmission Control
Module (TCM) Replacement in this section.

Did you complete the replacement?

—

Go to Step 18

—

1. Reconnect all previously disconnected

harness connector(s).

2. Clear the DTCs with the Tech 2.
3. Turn OFF the ignition for 30 seconds.
4. Lift the driving wheels or drive the vehicle.
5. Let the vehicle run within the Conditions for

Running the DTC.

Did the DTC fail this ignition?

—

Go to Step 3

Go to Step 19

Observe the DTC Information with the Tech 2.

Are there any DTCs that you have not diagnosed?

—

Go to Diagnostic

Trouble Code (DTC)

List

System OK

Step

Action

Value(s)

Yes

Transmission Control System (Smoother) 7A-85

P0718 (Flash Code 17)

Circuit Description
The gearshift clutch pulse width modulation (PWM)
solenoid valve is located on the oil pump assembly. It
controls the transmission fluid supply to the gearshift
clutch control spool valve. The transmission control
module (TCM) controls the gearshift clutch solenoid
valve by duty cycle signal based on vehicle running
condition. Since normally open type solenoid valve is
used, the gearshift clutch control spool valve moves by
the applied fluid pressure when the TCM turns OFF the
gearshift clutch solenoid valve under the certain
condition. Then the gearshift multi-plate clutch
engagement pressure circuit connects with the line
pressure circuit. At the same time, the gearshift multi-
plate clutch is engaged. The TCM detects the actual
state of the gearshift clutch solenoid valve by the slip
speed of the gearshift clutch based on the turbine speed
sensor signal and input shaft speed sensor signal
inputs. If the TCM detects an excessively low input shaft
speed in comparison to turbine speed, this DTC will set.
Condition for Running the DTC

• DTCs P0715 and P0717 are not set.
• The ignition switch is ON.
• The ignition voltage is more than 20 volts.
• The emergency switch is OFF.

Condition for Setting the DTC

• The TCM detects that the input shaft speed is less

than the turbine speed 300 RPM or more when the
gearshift clutch is commanded engage.

Action Taken When the DTC Sets

• The TCM illuminates the transmission warning

lamp when the diagnostic runs and fails.

• The TCM inhibits gear select & shift position

learning and half-clutch learning.

Condition for Clearing the DTC

• The TCM turns OFF the transmission warning

lamp when the diagnostic runs and does not fail.

• A current DTC clears when the diagnostic runs and

does not fail.

• A history DTC clears when the diagnostic runs and

does not fail.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

• Ensure the input shaft speed sensor is tight and the

counter shaft is not damaged.

• If this DTC is present, gearshift clutch slipping feel

will appear.

DTC P0718 (Flash Code 17)

Schematic Reference: Transmission Controls
Schematics
Connector End View Reference: Transmission
Controls Connector End Views or Transmission Control
Module (TCM) Connector End Views

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check -
Transmission Controls?

—

Go to Step 2

Go to Diagnostic

System Check -

Transmission

Controls

1. Inspect for correct ATF level. Refer to ATF

inspection in this section.

2. Inspect for external leakage.

Did you find and correct the condition?

—

Go to Step 10

Go to Step 3

1. Install the Tech 2.
2. Turn OFF the ignition for 30 seconds.
3. Lift the driving wheels or drive the vehicle.
4. Let the vehicle run within the Conditions for

Running the DTC.

5. Monitor the Diagnostic Trouble Code (DTC)

Information with the Tech 2.

Is DTC P0715, P0717, P0902 or P0903 set?

—

Go to Applicable

DTC

Go to Step 4

Let the vehicle run while observing the Turbine
Speed and Input Shaft Speed parameter with the
Tech 2.

Is the Input Shaft Speed parameter less than the
Turbine Speed 300 RPM or more?

—

Go to Step 5

Go to Diagnostic

Aids

Test the line pressure. Refer to line pressure test in
this section.

Does the line pressure within the specified value?

—

Go to Step 7

Go to Step 6

7A-86 Transmission Control System (Smoother)

1. Inspect oil strainer for clogging. Repair

Instructions (Overhaul) - Oil Filter in this
section.

2. Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 10

Go to Step 8

1. Remove the input shaft speed sensor. Refer to

Input Shaft Speed Sensor Replacement in this
section.

2. Visually inspect the input shaft speed sensor

for the following conditions:

• Physical damage
• Loose or improper installation

3. The following conditions may cause this DTC

to set:

• Excessive air gap between the input shaft

speed sensor and the counter shaft

• Electromagnetic interference in the input

shaft speed sensor circuits

• Foreign material passing between the

input shaft speed sensor and the counter
shaft

4. Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 10

Go to Step 8

1. Remove the oil pump assembly. Refer to

Repair Instructions (Overhaul) - Oil Pump in
this section.

2. Inspect the oil pump and gearshift clutch for

the following conditions:

• The oil pump for damage
• The gearshift clutch solenoid valve for

mechanically stuck or leaking

• The clutch spool valve mechanically stuck

or leaking

• The gasket or seal leaking or worn
• The band brake mechanically stuck

3. Repair or replace as necessary.

Did you find and correct the condition?

—

Go to Step 10

Go to Step 9

Important:
Replacement gearshift clutch assembly must be
learned.
Replace the gearshift clutch assembly. Refer to
Repair Instructions (Overhaul) - Gearshift Clutch
Replacement in this section.

Did you complete the replacement?

—

Go to Step 10

—

1. Reconnect all previously disconnected

harness connector(s).

2. Clear the DTCs with the Tech 2.
3. Turn OFF the ignition for 30 seconds.
4. Lift the driving wheels or drive the vehicle.
5. Let the vehicle run while observing the Turbine

Speed and Input Shaft Speed parameter with
the Tech 2.

Is the Input Shaft Speed parameter less than the
Turbine Speed 300 RPM or more?

—

Go to Step 2

Go to Step 11

Step

Action

Value(s)

Yes

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