Content .. 911 912 913 914 ..

Isuzu N-Series. Service manual - part 913

Transmission Control System (Smoother) 7A-107

1. Turn OFF the ignition.
2. Remove the smoother main relay.
3. Probe the battery voltage feed circuit of the

smoother main relay (pins 2 and 3 of X-5
connector) with a test lamp that is connected
to a known good ground.

Does the test lamp illuminate?

—

Go to Step 6

Go to Step 7

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

connections and corrosion at the harness
connector of the smoother main relay (pins 1,
2, 3 and 5 of X-5 connector).

3. Disconnect the transmission control module

(TCM) harness connector.

4. Inspect for an intermittent, for poor

connections and corrosion on the smoother
main relay control and voltage feed circuit at
the harness connector of the TCM (pin 15 of B-
425 and 3 of B-426 connector).

5. Test for high resistance on each smoother

main relay circuit.

6. Repair the connection(s) or circuit(s) as

necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

Repair the open circuit or high resistance on the
battery voltage feed circuit between the NEES (B)
(10A) fuse (F-13) in the glove box fuse block and
the smoother main relay (pins 2 and 3 of X-5
connector) (which ever test lamp did not illuminate
at Step 5). Check the NEES (B) (10 A) fuse (F-13)
first.

Did you complete the repair?

—

Go to Step 13

—

1. Turn OFF the ignition. Remove the smoother

main relay.

2. Turn ON the ignition, with the engine OFF.
3. Observe the Main Relay Voltage Feed Circuit

parameter with the Tech 2.

Does the Main Relay Voltage Feed Circuit
parameter indicate ON?

—

Go to Step 10

Go to Step 9

1. Test the control circuit of the smoother main

relay between the TCM (pin 15 of B-425
connector) and the smoother main relay (pin 5
of X-5 connector) for a short to ground.

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 voltage feed circuit between the TCM

(pin 3 of B-426 connector) and the smoother
main relay (pin 1 of X-5 connector) for a short
to battery.

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

Replace the smoother main relay.

Did you complete the replacement?

—

Go to Step 13

—

Step

Action

Value(s)

Yes

7A-108 Transmission Control System (Smoother)

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 fuse or

harness connector(s).

2. Clear the DTCs with the Tech 2.
3. Turn OFF the ignition for 30 seconds.
4. Turn ON the ignition, with the engine OFF.
5. Monitor the DTC Information with the Tech 2.

Did the DTC fail this ignition?

—

Go to Step 3

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-109

P0889 (Flash Code 39)

Circuit Description
The gearshift control box relay is energized to feed a
drive voltage of the each solenoid valve (1-3-5 shift
solenoid, 2-4-6-R shift solenoid and select solenoid)
when the transmission control module (TCM)
commands ON.
If the TCM detects the gearshift control box relay is
turned OFF when the relay is commanded ON, this DTC
will set. (Open stuck DTC)
If the TCM detects the TCM has been ON when the
relay is commanded OFF, this DTC will also set. (Close
stuck DTC)
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
Open stuck DTC

• The TCM detects a low voltage condition on the 1-

3-5 shift solenoid, 2-4-6-R shift solenoid and select
solenoid voltage feed circuit when the gearshift
control box relay is commanded ON.

Close stuck DTC

• The TCM detects a high voltage condition on the 1-

3-5 shift solenoid, 2-4-6-R shift solenoid and select
solenoid voltage feed circuit when the gearshift
control box relay is commanded OFF.

Action Taken When the DTC Sets

• The TCM illuminates the transmission warning

lamp when the diagnostic runs and fails.

• The TCM continuously sounds buzzer when the

diagnostic runs and fails. (Open stuck DTC)

• The TCM inhibits gearshift control. (Open stuck

DTC)

• The TCM holds gear position.
• 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.

• The TCM stops the buzzer when the diagnostic

runs and does not fail. (Open stuck DTC)

• 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.

Notice:

• If this DTC is present, P0912, P0973 and P0976

may also set.

• Faulty or sticking gearshift control box relay will set

this DTC.

DTC P0889 (Flash Code 39)

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.

Does the DTC fail this ignition?

—

Go to Step 3

Go to Diagnostic

Aids

1. Turn OFF the ignition.
2. Replace the gearshift control box relay with the

glow relay or replace with a known good relay.

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

Does the DTC fail this ignition?

—

Go to Step 4

Go to Step 11

Does the buzzer continuously sound?

—

Go to Step 5

Go to Step 8

7A-110 Transmission Control System (Smoother)

1. Turn OFF the ignition.
2. Remove the gearshift control box relay.
3. Probe the battery voltage feed circuit of the

gearshift control box relay (pins 3 and 4 of X-
19 connector) with a test lamp that is
connected to a known good ground.

Does the test lamp illuminate?

—

Go to Step 6

Go to Step 7

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

connections and corrosion at the harness
connector of the gearshift control box relay
(pins 2, 3, 4 and 5 of X-19 connector).

3. Disconnect the transmission control module

(TCM) harness connector.

4. Inspect for an intermittent, for a poor

connection and corrosion on gearshift control
box relay control circuit at the harness
connector of the TCM (pin 18 of B-425
connector).

5. Test the gearshift control box relay control

circuit for an open circuit or high resistance.

6. Test the each solenoid valve voltage feed

circuit between the gearshift control box relay
and the TCM (pins 4 and 5 of B-425, pins 5 and
6 of B-426 and pins 1 and 8 of B-418
connector) for an open circuit or high
resistance.

7. Repair the connection(s) or circuit(s) as

necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

Repair the open circuit or high resistance on the
battery voltage feed circuit between the NEES
(60A) slow blow fuse (SBF-7) and the gearshift
control box relay (pins 3 and 4 of X-19 connector)
(which ever test lamp did not illuminate at Step 5).
Check the NEES (60 A) slow blow fuse (SBF-7)
first.

Did you complete the repair?

—

Go to Step 13

—

1. Turn OFF the ignition.
2. Remove the gearshift control box relay.
3. Turn ON the ignition, with the engine OFF.

Does the buzzer continuously sound?

—

Go to Step 9

Go to Step10

1. Test the control circuit of the gearshift control

box relay between the TCM (pin 18 of B-425
connector) and the gearshift control box relay
(pin 5 of X-19 connector) for a short to ground.

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 voltage feed circuit between the TCM

(pins 4 and 5 of B-425, pins 5 and 6 of B-426
and pins 1 and 8 of B-418 connector) and the
gearshift control box relay (pin 2 of X-19
connector) for a short to battery.

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 13

Go to Step 12

Step

Action

Value(s)

Yes

Content .. 911 912 913 914 ..