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Isuzu N-Series. Manual - part 934

Transmission Control System (Smoother) 7A-191

Chart 4 of 4

Reconnect all previously disconnected fuse or
harness connector(s).

Is the action complete?

—

Go to Chart 1 of 4

Step 6

—

Step

Action

Value(s)

Yes

Step

Action

Value(s)

Yes

1. Turn ON the ignition, with the engine OFF.
2. Observe the Brake Pedal Switch parameter

with the Tech 2.

Does the Brake Pedal Switch parameter indicate
Applied when the pedal is applied and Released
when the pedal is released?

—

Go to Intermittent

Conditions

Go to Step 2

1. Check to ensure the brake pedal switch is

adjusted correctly. The plunger should be all
the way in when the pedal is released, yet
should not impede with the brake pedal full
upward travel.

2. Adjust the brake pedal switch as necessary.

Did you find and correct the condition?

—

Go to Step 22

Go to Step 3

1. Turn OFF the ignition.
2. Inspect the Stop Light (10A) fuse (F-5) in the

glove box fuse block.

Is the Stop Light (10A) fuse (F-5) open?

—

Go to Step 4

Go to Step 5

Replace the Stop Light (10A) fuse (F-5). If the fuse
continues to open, repair the short to ground on one
of the circuits that is fed by the Stop Light (10A) fuse
(F-5) or replace the shorted attached component
fed by the Stop Light (10A) fuse (F-5).

Did you complete the repair?

—

Go to Step 22

—

1. Turn OFF the ignition.
2. Disconnect the brake pedal switch harness

connector.

3. Connect a test lamp between the voltage feed

circuit of the brake pedal switch harness (pin 1
of B-66 connector) and a known good ground.

Does the test lamp illuminate?

—

Go to Step 6

Go to Step 7

1. Turn ON the ignition, with the engine OFF.
2. Observe the Brake Pedal Switch parameter

with the Tech 2 while momentarily jumping 3-
amp fused jumper wire across the brake pedal
switch harness connector between pins 1 and
2 of the B-66 connector.

Does the Tech 2 indicate Applied when the circuit is
jumpered and Released when the circuit is not
jumpered?

—

Go to Step 9

Go to Step 8

Repair the open circuit or high resistance on the
voltage feed circuit between the Stop Light (10A)
fuse (F-5) and the brake pedal switch (pin 1 of B-66
connector).

Did you complete the repair?

—

Go to Step 22

—

7A-192 Transmission Control System (Smoother)

1. Test the brake pedal switch signal circuit

between the transmission control module
(TCM) (pin 3 of B-428 connector) and the
brake pedal switch (pin 2 of B-66 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 22

Go to Step 10

1. Turn OFF the ignition.
2. Disconnect the brake pedal switch harness

connector.

3. Inspect for an intermittent and for poor

connections at the harness connector of the
brake pedal switch (pins 1 and 2 of B-66
connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 22

Go to Step 11

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

connection on the brake switch circuit at the
harness connector of the TCM (pin 3 of B-428
connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 22

Go to Step 21

Replace brake pedal switch.

Did you complete the replacement?

—

Go to Step 22

—

1. Turn OFF the ignition.
2. Disconnect the instrument panel cluster (IPC)

harness connector.

3. Inspect for an intermittent and for a poor

connection at the harness connector of the
IPC (pin 1 of B-53 connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 22

Go to Step 13

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

connection on the gear position display control
circuit at the harness connector of the TCM
(pin 14 of B-425 connector).

4. Repair the connection(s) as necessary.

Did you find and correct the condition?

—

Go to Step 22

Go to Step 14

1. Test the gear position display control circuit

between the TCM (pin 14 of B-425 connector)
and the IPC (pin 1 of B-53 connector) for the
following conditions:

• An open circuit
• A short to ground
• A short to battery or ignition voltage
• High resistance

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 22

Go to Step 15

Step

Action

Value(s)

Yes

Transmission Control System (Smoother) 7A-193

Replace the IPC. Refer to Instrument Panel Cluster
(IPC) Replacement in the Cab and Chassis
Electrical section.

Did you complete the replacement?

—

Go to Step 22

—

1. Turn ON the ignition, with the engine OFF.
2. Observe the PTO Switch parameter with the

Tech 2 in the ENGINE system menu.

Does the PTO Switch parameter OFF when the
PTO switch or lever is released?

—

Go to Intermittent

Conditions

Go to Step 17

1. Turn OFF the ignition.
2. Disconnect the PTO switch harness

connector.

3. Turn ON the ignition, with the engine OFF.
4. Observe the PTO Switch parameter with the

Tech 2.

Does the PTO Switch parameter OFF?

—

Go to Step 19

Go to Step 18

1. Test the PTO switch circuit between the ECM

(pin 44 of J-191 connector) and the PTO
switch or lever (pin 1 of B-84 connector) for a
short to ground.

2. Repair the circuit(s) as necessary.
3. Did you find and correct the condition?

—

Go to Step 22

Go to Step 20

Replace the PTO switch or lever.

Did you complete the replacement?

—

Go to Step 22

—

Important:
Replacement ECM must be programmed.
Replace the ECM. Refer to Engine Control Module
(ECM) Replacement /Restore Fuel Injector ID Code
Data in engine control section.

Did you complete the replacement?

—

Go to Step 22

—

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 22

—

Reconnect all previously disconnected fuse or
harness connector(s).

Is the action complete?

—

Go to Chart 1 of 4

Step 6

—

Step

Action

Value(s)

Yes

7A-194 Transmission Control System (Smoother)

Symptoms - Transmission Controls

Important Preliminary Inspections Before Starting
Perform Diagnostic System Check - Transmission
Controls before using the symptom tables, and verify
that all of the following are true:

• The transmission control module (TCM) and

transmission warning lamp are operating correctly.

• There are no diagnostic trouble codes (DTCs)

stored.

• The Tech 2 data is within the normal operating

range. Refer to Tech 2 Data List in this section.

• Verify the customer concern and locate the correct

symptom in the table of contents. Inspect the items
indicated under that symptom.

Visual and Physical Inspection
Several of the symptom procedures ask for careful
visual and physical inspection. This step is extremely
important. The visual and physical inspection can lead
to correcting a problem without further inspections, and
can save valuable time. Ensure that:

• The TCM grounds are clean, tight, and in their

proper location.

• The transmission harness wiring and terminals are

properly connected and are not pinched or cut.

Intermittent

Important:
Inspect for improper installation of electrical
components if an intermittent condition exists. Inspect
for aftermarket add-on electrical equipment devices,
lights, and cellular phones. Verify that no aftermarket
equipment is connected to the keyword 2000 serial data
circuit. If you cannot locate an intermittent condition, a
cellular phone communication signal may cause the
condition.

Important:
The problem may or may not turn ON the transmission
warning lamp or store a DTC.
Faulty electrical connections or wiring cause most
intermittent problems. Perform a careful visual and
physical inspection of the suspect connectors for the
following conditions:

• Improperly mated connector halves
• Terminals that are not seated
• Terminals that are damaged or improperly formed

Reform or replace connector terminals in the problem
circuit in order to ensure proper contact tension.
Remove the terminal from the connector body in order
to inspect for poor terminal wire connection.
Road test the vehicle with the DMM connected to the
suspected circuit. An abnormal reading that occurs
when the malfunction occurs is a good indication that
there is a malfunction in the circuit being monitored.

Use the Tech 2 in order to help detect intermittent
conditions. Useful features of the Tech 2 include the
following:

• Trigger the Snapshot feature in order to capture

and store transmission parameters when the
malfunction occurs. Review this stored information
in order to see the specific running conditions that
caused the malfunction.

• Use the Plot Function on the Tech 2 in order to plot

selected data parameters. Review this stored
information to aid in locating an intermittent
problem. Refer to the Tech 2 Users Guide for more
information.

Important:
If the intermittent condition exists as a start and then
stall, test for DTCs relating to the vehicle theft deterrent
system. Test for improper installation of electrical
options such as lights, cellular phones, etc.
Any of the following may cause an intermittent
transmission warning lamp with no stored DTC:

• The TCM grounds are loose or dirty. Refer to

Transmission Controls Schematics.

• The transmission warning lamp circuit

intermittently shorted to ground.

• Electrical system interference caused by a

malfunctioning relay, TCM driven solenoid, or
switch. The electrical component can cause a
sharp electrical surge. Normally, the problem will
occur when the malfunctioning component is
operating.

• There are any open diodes.

Important:
The following symptom tables contain groups of
possible causes for each symptom. The order of these
procedures is not important. If the Tech 2 readings do
not indicate the problems, then proceed in a logical
order, easiest to check or most likely to cause first. In
order to determine if a specific vehicle is using a
particular system or component, refer to Transmission
Controls Schematics for an application.
Use the following tables when diagnosing a symptom
complaint:

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