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Isuzu N-Series. Manual - part 922

Transmission Control System (Smoother) 7A-143

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.

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

7A-144 Transmission Control System (Smoother)

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

Transmission Control System (Smoother) 7A-145

P0973 (Flash Code 71)

Circuit Description
The pulse width modulation (PWM) 2-4-6-R shift
solenoid valve is located on the gearshift control box.
The transmission control module (TCM) controls the 2-
4-6-R shift solenoid valve by duty cycle signal based on
commanded gear position. 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 a high voltage condition on
the 2-4-6-R shift solenoid valve monitor circuit when the
solenoid valve is commanded OFF, this DTC will set.
Condition for Running the DTC

• DTC P0889 is 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.

Condition for Setting the DTC

• The TCM detects a high voltage condition on the 2-

4-6-R shift solenoid valve monitor circuit when the
solenoid valve is commanded OFF.

Action Taken When the DTC Sets

• The TCM illuminates the transmission warning

lamp when the diagnostic runs and fails.

• The TCM intermittently sounds buzzer when the

diagnostic runs and fails.

• The TCM commands OFF gearshift control box

relay.

• The TCM inhibits gearshift control and holds gear

position 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 at
next ignition cycle

• The TCM stops the buzzer 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.

• A history DTC clears with the Tech 2 or reset

switch operation.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

DTC P0973 (Flash Code 71)

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. Turn ON the ignition, with the engine OFF.
4. Monitor the Diagnostic Trouble Code (DTC)

Information with the Tech 2.

Is DTC P0889 also set?

—

Go to DTC P0889

Go to Step 3

1. Turn OFF the ignition for 30 seconds.
2. Disconnect the 2-4-6-R shift solenoid valve

harness connector.

3. Connect a DMM between the control circuit of

the 2-4-6-R shift solenoid valve harness (pin 2
of J-236 connector) and a known good ground.

4. Turn ON the ignition, with the engine OFF.

Is the DMM voltage more than the specified value
until this DTC fails?

18.0 volts

Go to Step 4

Go to Step 6

Is the DMM voltage more than the specified value
after this DTC fails?

18.0 volts

Go to Step 7

Go to Step 5

7A-146 Transmission Control System (Smoother)

1. Connect a test lamp between the ground

circuit of the 2-4-6-R shift solenoid valve
harness (pin 1 of J-236 connector) and battery
voltage.

2. Turn ON the ignition.

Does the test lamp illuminate?

—

Go to Step 9

Go to Step 8

1. Test the voltage feed circuit between the

transmission control module (TCM) (pins 5
and 6 of B-426 connector) and the gearshift
control box relay (pin 2 of X-19 connector) for
an open circuit or high resistance.

2. Test the control circuit between the TCM (pins

8 and 9 of B-425 connector) and the 2-4-6-R
shift solenoid (pin 2 of J-236 connector) for an
open circuit or high resistance.

3. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 10

Important:
The 2-4-6-R shift solenoid valve may be damaged if
the solenoid valve control circuit is shorted to a
voltage source.

1. Test the control circuit between the TCM (pins

8 and 9 of B-425 connector) and the 2-4-6-R
shift solenoid (pin 2 of J-236 connector) 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

1. Test the ground circuit between 2-4-6-R shift

solenoid (pin 1 of J-236 connector) and
chassis ground (J-9) for an open circuit or high
resistance.

2. Test the ground circuit between the TCM (pins

1 and 2 of B-425 connector) and chassis
ground (J-9) for an open circuit or high
resistance.

3. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 10

1. Turn OFF the ignition.
2. Disconnect the 2-4-6-R shift solenoid valve

harness connector.

3. Inspect for an intermittent and for poor

connections at the harness connector of the 2-
4-6-R shift solenoid valve (pins 1 and 2 of J-
236 connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 11

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

connections on the 2-4-6-R shift solenoid
circuits at the harness connector of the TCM
(pins 1, 2, 8 and 9 of B-425 and pins 5 and 6 of
B-426 connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

Step

Action

Value(s)

Yes

Content .. 920 921 922 923 ..