Isuzu KB P190. Manual - part 1094

7A2-92 TRANSMISSION CONTROL SYSTEM (JR405E)

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 TCM and check trans lamp is operating

correctly.

• The scan tool data is within the normal operating

range. Refer to Scan Tool 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 serial data circuit.
Important: The problem may or may not turn ON the
check trans 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 scan tool in order to help detect intermittent
conditions. Useful features of the Tech 2 includes 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 scan tool in order to

plot selected data parameters. Review this stored
information to aid in locating an intermittent
problem. Refer to the scan tool 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 check
trans lamp with no stored DTC:

• The TCM grounds are loose or dirty. Refer to

Transmission Controls Schematics.

• The check trans 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 scan
tool 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:

• Intermittent Conditions

• Vehicle Does Not Run

• Trouble at Starting

• Faulty Gearshift

• Faulty Shift Pattern

• No or Error Gearshift

• Faulty Operation During Running

• Faulty Operation in Stopping

• Faulty Lock Up

• No Lock Up

• Transmission Fluid Leak

• Others

TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-93

Intermittent Conditions

Checks

Action

Definition:
The problem is not currently present but is indicated in DTC History.
OR
There is a customer complaint, but the symptom cannot currently be duplicated, if the problem is not DTC related.

Preliminary Checks

• Refer to Symptoms - Transmission Controls before starting.

Harness/ Connector

Many intermittent open or shorted circuits are affected by harness/ connector
movement that is caused by vibration, engine torque, bumps/ rough pavement, etc.
Test for this type of condition by performing the applicable procedure from the
following list:

• Move related connectors and wiring while monitoring the appropriate scan tool

data.

• Move related connectors and wiring with the component commanded ON, and

OFF, with the scan tool. Observe the component operation.

• With the engine running, move related connectors and wiring while monitoring

engine operation.

If harness or connector movement affects the data displayed, component/ system
operation, or engine operation, inspect and repair the harness/ connections as
necessary.

Electrical Connections or Wiring

Poor electrical connections, terminal tension or wiring problems cause most
intermittent. To perform the following inspections:

• Poor mating of the connector halves, or terminals improperly seated in the

connector body.

• Improperly formed or damaged terminals. Test for poor terminal tension.

• Poor terminal to wire connections including terminals crimped over insulation.

This requires removing the terminal from the connector body.

• Corrosion/ water intrusion. Pierced or damaged insulation can allow moisture to

enter the wiring. The conductor can corrode inside the insulation, with little
visible evidence. Look for swollen and stiff sections of wire in the suspect
circuits.

• Wires that are broken inside the insulation.

• Harness for pinched, cut or rubbed through wiring.

• Ensure that the wiring does not come in contact with hot exhaust components.

Control Module Power and Grounds
Component Power and Grounds

Poor power or ground connections can cause widely varying symptoms.

• Test all control module power supply circuits. Many vehicles have multiple

circuits supplying power to the control module. Other components in the system
may have separate power supply circuits that may also need to be tested.
Inspect connections at the module/ component connectors, fuses, and any
intermediate connections between the power source and the module/
component. A test lamp or a DMM may indicate that voltage is present, but
neither tests the ability of the circuit to carry sufficient current. Ensure that the
circuit can carry the current necessary to operate the component.

• Test all control module ground and system ground circuits. The control module

may have multiple ground circuits. Other components in the system may have
separate grounds that may also need to be tested. Inspect grounds for clean
and tight connections at the grounding point. Inspect the connections at the
component and in splice packs, where applicable. Ensure that the circuit can
carry the current necessary to operate the component.

7A2-94 TRANSMISSION CONTROL SYSTEM (JR405E)

Temperature Sensitivity

• An intermittent condition may occur when a component/ connection reaches

normal operating temperature. The condition may occur only when the
component/ connection is cold, or only when the component/ connection is hot.

• If the intermittent is related to heat, review the data for a relationship with the

following:

- High ambient temperatures.

- Underhood/ engine generated heat.

- Circuit generated heat due to a poor connection, or high electrical load.

- Higher than normal load conditions, towing, etc.

• If the intermittent is related to cold, review the data for the following:

- Low ambient temperatures-In extremely low temperatures, ice may form in a

connection or component. Test for water intrusion.

- The condition only occurs on a cold start.

- The condition goes away when the vehicle warms up.

• Information from the customer may help to determine if the trouble follows a

pattern that is temperature related.

Electromagnetic Interference (EMI) and
Electrical Noise

Some electrical components/ circuits are sensitive to EMI or other types of electrical
noise. Inspect the following conditions:

• A misrouted harness that is too close to high voltage/ high current devices such

as injection components, motors, generator etc. These components may
induce electrical noise on a circuit that could interfere with normal circuit
operation.

• Electrical system interference caused by a malfunctioning relay, or the TCM

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

• Improper installation of non-factory or aftermarket add on accessories such as

lights, 2-way radios, amplifiers, electric motors, remote starters, alarm systems,
cell phones, etc. These accessories may lead to an emission related failure
while in use, but do not fail when the accessories are not in use.

• Test for any open diodes. Some relays may contain a clamping diode.

• Test the generator for a bad rectifier bridge that may be allowing AC noise into

the electrical system.

Incorrect TCM Programming

• There are only a few situations where reprogramming a TCM is appropriate:

- An ECM from another vehicle is installed.

- Revised software/ calibration files have been released for this vehicle.

Important: DO NOT reprogram the TCM with the SAME software/ calibration files
that are already present in the TCM. This is not an effective repair for any type of
driveability problem.

• Verify that the TCM contains the correct software/ calibration. If incorrect

programming is found, reprogram the TCM with the most current software/
calibration.

Duplicating Failure Conditions

• If none of the previous tests are successful, attempt to duplicate and/ or capture

the failure conditions.

• An alternate method is to drive the vehicle with the DMM connected to a

suspected circuit. An abnormal reading on the DMM when the problem occurs,
may help you locate the problem.

Scan Tool Snapshot

The scan tool can be set up to take a Snapshot of the parameters available via serial
data. The Snapshot function records live data over a period of time. The recorded
data can be played back and analyzed. The scan tool can also graph parameters
singly or in combinations of parameters for comparison. The Snapshot can be
triggered manually at the time the symptom is noticed, or set up in advance to trigger
when a DTC sets.
An abnormal value captured in the recorded data may point to a system or
component that needs to be investigated further.
Refer to the scan tool Users Guide for more information.

Checks

Action

TRANSMISSION CONTROL SYSTEM (JR405E) 7A2-95

Vehicle Does Not Run

Trouble at Starting

Faulty Gearshift

Faulty Shift Pattern

No or Error Gearshift

Faulty Operation During Running

Faulty Operation in Stopping

Faulty Lock Up

No Lock Up

Transmission Fluid Leak

Others

Diagnostic Category

Category No.

This table consists of diagnostic categories that are located in the left column. Using this column, choose the appropriate
category based on the operating conditions of the vehicle or transmission. After selecting a category, use the right column to
locate the specific symptom diagnostic information.

Vehicle Does Not Run

Vehicle does not run in D, 3, 2, L & L range

Vehicle does not run in R range

Vehicle does not run in D, 3, 2 and L range

Trouble at Starting

Vehicle runs in N range

Poor acceleration at starting

Engine races up during starting (slip)

Large shock when selector lever is changed from N to D range or N to R
range

Engine stalls when selector lever is changed from N to R, D, 3, 2 or L
range

Engine does not crank in P or N range

Engine cranks in other than P or N range

Extended time lag when selector lever is changed from N to D

Extended time lag when selector lever is changed from N to R

Brake is applied in R range

B10

Insufficient starting or shaking in D range

B11

Noise or vibration occurs at starting

B12

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