Isuzu N-Series. Manual - part 915

Transmission Control System (Smoother) 7A-115

1. Keep the test lamp with connected.
2. Turn OFF the ignition for 30 second.
3. Start the engine while observing the test lamp.

Does the test lamp blink after the engine start (note
that the test lamp will blink then continuously
illuminate normally)?

—

Go to Step 7

Go to Step 6

1. Test the control circuit of the gearshift clutch

solenoid valve between the transmission
control module (TCM) (pin 30 of B-425
connector) and the in-line harness connector
(pin 3 of J-237 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 12

Go to Step 8

1. Test the control circuit of the gearshift clutch

solenoid valve between the TCM (pin 30 of B-
425 connector) and the in-line harness
connector (pin 3 of J-237 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 12

Go to Step 11

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

connection at the in-line harness connector
(pin 3 of J-237 connector).

3. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 12

Go to Step 9

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

connection on the gearshift clutch solenoid
valve circuit at the harness connector of the
TCM (pin 30 of B-425 connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 12

Go to Step 11

1. Remove the oil pump assembly. Refer to

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

2. Inspect for an intermittent and for a poor

connection at the harness connector of the
gearshift clutch solenoid valve.

3. Inspect the gearshift clutch solenoid valve for

loose bolt.

4. Test the control circuit of the gearshift clutch

solenoid valve between the gearshift clutch
solenoid valve and the in-line harness
connector (pin 3 of J-237 connector) for the
following conditions:

• An open circuit
• A short to the lock up clutch solenoid valve

control circuit

• High resistance

5. Repair the circuit(s), connection(s) or tightness

as necessary.

Did you find and correct the condition?

—

Go to Step 12

Go to Step 10

Step

Action

Value(s)

Yes

7A-116 Transmission Control System (Smoother)

Important:
Replacement gearshift clutch solenoid valve must
be learned.
Replace the gearshift clutch solenoid valve. Refer to
Repair Instructions (Overhaul) - Oil Pump in this
section.

Did you complete the replacement?

—

Go to Step 12

—

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 12

—

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 and D

to N.

7. Monitor the DTC Information with the Tech 2.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Step 13

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-117

P0904 (Flash Code 58)

Circuit Description
The gear select position sensor is used to detect the
select side lever position feedback for the select
solenoid valve on the transmission gearshift control box
and it is installed to the transmission gearshift control
box assembly. The transmission control module (TCM)
uses the gear select position sensor to determine the
current gear position with a combination of the gear shift
position sensor. The gear select position sensor has
following circuits.

• 5 volts reference circuit
• Low reference circuit
• Gear select position sensor signal circuit

The TCM supplies 5 volts to the gear select position
sensor on the 5 volts reference circuit. The TCM also
provides a ground on the low reference circuit. The gear
select position sensor provides a signal to the TCM on
the gear select position sensor signal circuit, which is
relative to the position changes of the select side. The
TCM monitors the gear select position sensor signal for
voltages outside the normal range of the gear select
position sensor. If the ECM detects an excessively low
or high gear select position sensor voltage, 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

• The TCM detects that the gear select position

sensor signal voltage is less than 0.5 volts or more
than 4.5 volts.

Action Taken When the DTC Sets

• The TCM illuminates the transmission warning

lamp when the diagnostic runs and fails.

• The TCM inhibits auto shift control.
• The TCM permits shifting to neutral, 1st or reverse

gear.

• 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 the sensor is tight, the sensor shaft and

sensor lever are not damaged.

Notice:

• If this DTC is present, the Gear Select Position

Sensor parameters on the Tech 2 will indicate
desired value.

DTC P0904 (Flash Code 58)

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.

Notice:
If the gear select position sensor signal voltage is
more than 4.5 volts, the Gear Select Position Sensor
parameter on the Tech 2 indicates a desired value
when the ignition has been turned ON for longer
than 5 seconds.

Does the Gear Select Position Sensor parameter
ever exceed the specified value within 5 seconds
after the ignition switch is ON?

4.5 volts

Go to Step 4

Go to Step 3

7A-118 Transmission Control System (Smoother)

Notice:
If the gear select position sensor signal is less than
0.5 volts, the Gear Select Position Sensor parameter
on the Tech 2 indicates a desired value when the
ignition has been turned ON for longer than 5
seconds.

Does the Gear Select Position Sensor parameter
ever fall below the specified value within 5 seconds
after the ignition switch is ON?

0.5 volts

Go to Step 7

Go to Diagnostic

Aids

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

harness connector.

3. Turn ON the ignition, with the engine OFF.
4. Observe the Gear Select Position Sensor

parameter with the Tech 2.

Is the Gear Select Position Sensor parameter less
than the specified value within 5 seconds after the
ignition switch is ON?

0.5 volts

Go to Step 5

Go to Step 9

1. Turn OFF the ignition.
2. Connect a DMM between the 5 volts reference

circuit of the gear select position sensor
harness (pin 1 of J-223 connector) and a
known good ground.

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

Is the DMM voltage less than the specified value?

5.5 volts

Go to Step 6

Go to Step 10

1. Turn OFF the ignition.
2. Connect a test lamp between the low

reference circuit of the gear select position
sensor harness (pin 3 of J-223 connector) and
battery voltage.

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

Does the test lamp illuminate?

—

Go to Step 14

Go to Step 11

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

harness connector.

3. Connect a DMM between the 5 volts reference

circuit of the gear select position sensor
harness (pin 1 of J-223 connector) and a
known good ground.

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

Is the DMM voltage more than the specified value?

4.5 volts

Go to Step 8

Go to Step 12

1. Turn OFF the ignition.
2. Connect a 3-amp fused jumper wire between

the 5 volts reference circuit and the signal
circuit of the gear select position sensor
harness (pin 1 and 2 of J-223 connector).

3. Turn ON the ignition, with the engine OFF.
4. Observe the Gear Select Position Sensor

parameter with the Tech 2.

Is the Gear Select Position Sensor parameter more
than the specified value within 5 seconds after the
ignition switch is ON?

4.5 volts

Go to Step 14

Go to Step 13

Step

Action

Value(s)

Yes

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