Isuzu N-Series. Manual — part 916

Transmission Control System (Smoother) 7A-119

9

Important:
The gear select position sensor may be damaged if
the sensor signal circuit is shorted to a voltage
source.

1. Test the signal circuit between the

transmission control module (TCM) (pin 11 of
B-426 connector) and the gear select position
sensor (pin 2 of J-223 connector) for the
following conditions:

• A short to battery or ignition voltage
• A short to any 5 volts reference

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 18

10

1. Test the 5 volts reference circuit between the

TCM (pin 10 of B-426 connector) and the gear
select position sensor (pin 1 of J-223
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 19

Go to Step 18

11

1. Test the low reference circuit between the

TCM (pin 13 of B-426 connector) and the gear
select position sensor (pin 3 of J-223
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 19

Go to Step 15

12

1. Test the 5 volts reference circuit between the

TCM (pin 10 of B-426 connector) and the gear
select position sensor (pin 1 of J-223
connector) for the following conditions:

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

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 15

13

1. Test the signal circuit between the TCM (pin

11 of B-426 connector) and the gear select
position sensor (pin 2 of J-223 connector) for
the following conditions:

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

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 15

Step

Action

Value(s)

Yes

No

7A-120 Transmission Control System (Smoother)

14

1. Turn OFF the ignition.
2. Disconnect the gear select position sensor

harness connector.

3. Inspect for an intermittent and for poor

connections at the harness connector of the
gear select position sensor (pins 1, 2 and 3 of
J-223 connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 16

15

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

connections on the gear select position sensor
circuits at the harness connector of the TCM
(pins 10, 11 and 13 of B-426 connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 18

16

1. Remove the gear select position sensor. Refer

to Gear Select Position Sensor Replacement
in this section.

2. Visually inspect the gear select position sensor

for the following conditions:

• Physical damage
• Loose or improper installation

3. Remove the transmission gearshift control box

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

4. Visually inspect the lever for damage that

connects to the gear select position sensor
shaft.

Did you find and correct the condition?

—

Go to Step 19

Go to Step 17

17

Important:
Replacement gear select position sensor must be
learned.
Replace the gear select position sensor. Refer to
Gear Select Position Sensor Replacement in this
section.

Did you complete the replacement?

—

Go to Step 19

—

18

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 19

—

19

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.

Did the DTC fail this ignition?

—

Go to Step 2

Go to Step 20

Step

Action

Value(s)

Yes

No

Transmission Control System (Smoother) 7A-121

20

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

No

7A-122 Transmission Control System (Smoother)

P0906 (Flash Code 52)

Circuit Description
The selector lever switches are installed to the selector
lever bracket and there are two switches. The forward
and backward direction switch detects the selector lever
forward and backward movement. The horizontal
direction switch detects the selector lever horizontal
movement. When the selector lever is positioned N, D or
R, each selector lever switch is closed and the switch
signal from the transmission control module (TCM) is
pulled to ground. When the selector lever is positioned
A, + or

−, each selector lever switch and D switch are

also closed and the switch signal from the TCM is pulled
to ground. If the TCM detects the selector lever switch
input signal is out of correlation, this DTC will set.
Condition for Running the DTC

• The ignition switch is ON.
• The ignition voltage is more than 20 volts.
• The emergency switch is OFF.

Condition for Setting the DTC
Either of following condition is met:

• The TCM detects two or more selector lever N, D

and R switch signal is ON (pulled to ground).

• The TCM detects two or more selector lever A, +

and

− switch signal is ON (pulled to ground) when

the selector lever N, D or R switch signal is ON
(pulled to ground).

Action Taken When the DTC Sets

• The TCM illuminates the transmission warning

lamp when the diagnostic runs and fails.

• The TCM inhibits selector lever switch signal.
• 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 with the Tech 2 or reset

switch operation.

Diagnostic Aids

• If an intermittent condition is suspected, refer to

Intermittent Conditions in this section.

• Ensure each selector lever switch is tight and not

damaged.

DTC P0906 (Flash Code 52)

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

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 the Tech 2.
2. Turn ON the ignition, with the engine OFF.
3. Operate the selector lever while observing the

Selector N, R, D, A, + and

− Switch parameter

with the Tech 2.

Notice:
The Selector D Switch parameter indicates ON
when the selector lever is A, + or

− .

Does each selector lever switch parameter display
ON when it moved to its position and display OFF
when it moved to other positions?

—

Go to Diagnostic

Aids

Go to Step 3

3

1. Turn OFF the ignition.
2. Remove the selector lever cover.
3. Disconnect the selector lever switch harness

connector.

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

Does all selector position switch parameter display
OFF?

—

Go to Step 5

Go to Step 4