Isuzu N-Series. Manual - part 921

Transmission Control System (Smoother) 7A-139

P0915 (Flash Code 74)

Circuit Description
The pulse width modulation (PWM) 1-3-5 and 2-4-6-R
shift solenoid valves are located on the gearshift control
box. The transmission control module (TCM) controls
each shift solenoid valves by duty cycle signal based on
commanded gear position. The 1-3-5 shift solenoid is
commanded ON when the commanded gear is set to
1st, 3rd and 5th gear. When disengaging from 2nd, 4th,
6th and reverse gear, the 1-3-5 shift solenoid is also
commanded ON. The 2-4-6-R shift solenoid is
commanded ON when the commanded gear is set to
2nd, 4th, 6th and reverse gear. When disengaging
from1st, 3rd and 5th gear, the 2-4-6-R shift solenoid is
also commanded ON. The gear shift position sensor is
used to detect the shift side lever position feedback for
the shift solenoid valves movement. The TCM uses the
gear shift position sensor to determine the current gear
position with a combination of the gear select position
sensor. If the TCM detects the gear shift side lever
position does not reach to a desired shift position and it
keeping a previous gear position when shifting to
desired gear, this DTC will set.
Condition for Running the DTC

• DTCs P0718, P0889, P0902, P0903, P0904,

P0912, P0913, P0914, P0973, P0974, P0976 and
P0977 are not set.

• The ignition switch is ON.
• The ignition voltage is more than 20 volts.
• The emergency switch is OFF.
• The gearshift control box relay is commanded ON.
• The selector lever is other than N position.

Condition for Setting the DTC

• The TCM detects the gear shift side lever position

does not reach to a desired shift position and it
keeping a previously engaged gear position
continuously when shifting to desired gear. This
indicates that the TCM detects gear stuck at an
engaged position.

Action Taken When the DTC Sets

• The TCM illuminates the transmission warning

lamp when the diagnostic runs and fails.

• The TCM inhibits gearshift control.
• The TCM commands OFF the gearshift clutch

solenoid valve.

• The TCM commands OFF the lock up clutch

solenoid valve.

• 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.

DTC P0915 (Flash Code 74)

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. 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 so that all gear may engage

enough.

5. Monitor the Diagnostic Trouble Code (DTC)

Information with the Tech 2.

Is P0902, P0903, P0904, P0912, P0913, P0914,
P0973, P0974, P0976 or P0977 also set?

—

Go to Applicable

DTC

Go to Step 3

Visually inspect the gear shift position sensor, 1-3-5
and 2-4-6-R shift solenoid valves for the following
conditions:
• Physical damage
• Loose or improper installation

Did you find and correct the condition?

—

Go to Step 8

Go to Step 4

7A-140 Transmission Control System (Smoother)

1. Lift the driving wheels or drive the vehicle.
2. Let the vehicle run so that all gear may engage

enough.

3. Monitor the DTC Information with the Tech 2.

Does the DTC fail this ignition?

—

Go to Step 5

Go to Diagnostic

Aids

1. Remove the gear shift position sensor. Refer

to Gear Shift Position Sensor Replacement in
this section.

2. Visually inspect the gear shift position sensor

for the following conditions:

• Physical damage
• Loose or improper installation

3. Inspect the gear shift position sensor output

voltage in order to check an open circuit, short
circuit and high resistance somewhere in the
operating range.

4. Remove the transmission gearshift control box

assembly from the transmission main unit.
Refer to Repair Instructions (Overhaul) -
Control Box in this section.

5. Visually inspect the shift side lever for the

following conditions:

• Shift lever damage that connects to the

gear shift position sensor shaft.

• Shift lever damage that connects to the

shift solenoid valves.

• Shift lever damage that connects to the

interlock plate and shift rods.

• Other damage that the shift lever possible

stuck.

6. Inspect the transmission main unit as

necessary. Refer to Repair Instructions
(Overhaul) in this section.

7. Repair or replace as necessary.
8. Did you find and correct the condition?

—

Go to Step 8

Go to Step 6

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 gearshift clutch solenoid valve for

mechanically stuck

• The clutch spool valve mechanically stuck
• The gearshift clutch mechanically stuck

3. Repair or replace as necessary.

Did you find and correct the condition?

Go to Step 8

Go to Step 7

Important:
Replacement 1-3-5 or 2-4-6-R shift solenoid valve
must be relearned.
Replace the 1-3-5 or 2-4-6-R shift solenoid valve.
Refer to Repair Instructions (Overhaul) - Gearshift
Control Box in this section.

Did you complete the replacement?

—

Go to Step 8

—

Step

Action

Value(s)

Yes

Transmission Control System (Smoother) 7A-141

1. Reconnect all previously disconnected

harness connector(s).

2. Clear the DTCs with the Tech 2.

Important:
Transmission Gear Select & Shift Position Learning
must be done if the gear shift position sensor, 1-3-5
shift solenoid valve, 2-4-6-R shift solenoid valve or
transmission gearshift control box is replaced,
removed or repaired.

Important:
Half-clutch Position Learning must be done if the
gearshift clutch is replaced, removed or repaired.

3. Turn OFF the ignition for 30 seconds.
4. Lift the driving wheels or drive the vehicle.
5. Let the vehicle run so that all gear may engage

enough.

6. Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 9

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

7A-142 Transmission Control System (Smoother)

P0919 (Flash Code 72)

Circuit Description
The pulse width modulation (PWM) 1-3-5 and 2-4-6-R
shift solenoid valves are located on the gearshift control
box. The transmission control module (TCM) controls
each shift solenoid valves by duty cycle signal based on
commanded gear position. The 1-3-5 shift solenoid is
commanded ON when the commanded gear is set to
1st, 3rd and 5th gear. When disengaging from 2nd, 4th,
6th and reverse gear, the 1-3-5 shift solenoid is also
commanded ON. The 2-4-6-R shift solenoid is
commanded ON when the commanded gear is set to
2nd, 4th, 6th and reverse gear. When disengaging
from1st, 3rd and 5th gear, the 2-4-6-R shift solenoid is
also commanded ON. The gear shift position sensor is
used to detect the shift side lever position feedback for
the shift solenoid valves movement. The TCM uses the
gear shift position sensor to determine the current gear
position with a combination of the gear select position
sensor. If the TCM detects the gear shift side lever
position does not reach to a desired shift position when
shifting to desired gear, this DTC will set.
Condition for Running the DTC

• DTCs P0718, P0889, P0902, P0903, P0904,

P0912, P0913, P0914, P0973, P0974, P0976 and
P0977 are not set.

Condition for Setting the DTC

• The TCM detects the gear shift side lever position

does not reach to a desired shift position
continuously when shifting to desired gear.

Action Taken When the DTC Sets

• The TCM illuminates the transmission warning

lamp when the diagnostic runs and fails.

• The TCM inhibits gearshift control.
• The TCM commands OFF the gearshift clutch

solenoid valve.

• The TCM commands OFF the lock up clutch

solenoid valve.

• 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.

DTC P0919 (Flash Code 72)

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. 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 so that all gear may engage

enough.

5. Monitor the Diagnostic Trouble Code (DTC)

Information with the Tech 2.

Is P0902, P0903, P0904, P0912, P0913, P0914,
P0973, P0974, P0976 or P0977 also set?

—

Go to Applicable

DTC

Go to Step 3

Visually inspect the gear shift position sensor, 1-3-5
and 2-4-6-R shift solenoid valves for the following
conditions:
• Physical damage
• Loose or improper installation

Did you find and correct the condition?

—

Go to Step 8

Go to Step 4

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