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Isuzu N-Series. Service manual - part 919

Transmission Control System (Smoother) 7A-131

1. Connect a test lamp between the ground

circuit of the select solenoid valve harness (pin
1 of J-234 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 1
and 8 of B-428 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

16 and 22 of B-428 connector) and the select
solenoid (pin 2 of J-234 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 select 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

16 and 22 of B-428 connector) and the select
solenoid (pin 2 of J-234 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 the select

solenoid (pin 1 of J-234 connector) and
chassis ground (J-9) for an open circuit or high
resistance.

2. Test the ground circuit between the TCM (pins

7 and 15 of B-428 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 select solenoid valve harness

connector.

3. Inspect for an intermittent and for poor

connections at the harness connector of the
select solenoid valve (pins 1 and 2 of J-234
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 select solenoid valve
circuits at the harness connector of the TCM
(pins 1, 7, 8, 15 16 and 22 of B-428 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

7A-132 Transmission Control System (Smoother)

Important:
Replacement select solenoid valve must be learned.
Replace the select solenoid valve. Refer to Repair
Instructions (Overhaul) - Gearshift Control Box in
this section.

Did you complete the replacement?

—

Go to Step 13

—

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 13

—

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. Start the engine.
5. Operate the vehicle within the Conditions for

Running the DTC.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 14

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-133

P0913 (Flash Code 75)

Circuit Description
The pulse width modulation (PWM) select solenoid
valve is located on the gearshift control box. The
transmission control module (TCM) controls the select
solenoid valve by duty cycle signal based on
commanded gear position. The select solenoid is only
commanded ON when up-shifting. When downshifting,
the force created by the return springs moves the
internal select lever, but the select solenoid limits the
amount of movement by generating force as required in
the up-shift direction. The gear select position sensor is
used to detect the select side lever position feedback for
the select solenoid valve movement. The TCM uses the
gear select position sensor to determine the current
gear position with a combination of the gear shift
position sensor. If the TCM detects a low voltage
condition on the select solenoid valve monitor circuit
when the solenoid valve is commanded ON, 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 low voltage condition on the

select solenoid valve monitor circuit when the
solenoid valve is commanded ON.

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 P0913 (Flash Code 75)

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. Place the transmission in neutral and set the

parking brake.

4. Start the engine.
5. Operate the selector lever from N to D in order

to shift to 2nd or higher gear.

6. Monitor the Diagnostic Trouble Code (DTC)

Information with the Tech 2.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic

Aids

1. Turn OFF the ignition for 30 seconds.
2. Disconnect the select solenoid valve harness

connector.

3. Turn ON the ignition, with the engine OFF.
4. Monitor the DTC Information with the Tech 2.

Is DTC P0912 set?

—

Go to Step 5

Go to Step 4

7A-134 Transmission Control System (Smoother)

1. Test the control circuit between the

transmission control module (TCM) (pins 16
and 22 of B-428 connector) and the select
solenoid valve (pin 2 of J-234 connector) for a
short to ground.

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 7

Go to Step 6

Important:
Replacement select solenoid valve must be learned.
Replace the select solenoid valve. Refer to Repair
Instructions (Overhaul) - Gearshift Control Box in
this section.

Did you complete the replacement?

—

Go to Step 7

—

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 7

—

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. Place the transmission in neutral and set the

parking brake.

5. Start the engine.
6. Operate the selector lever from N to D in order

to shift to 2nd or higher gear.

7. Monitor the DTC Information with the Tech 2.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Step 8

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

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