1998 ISUZU TROOPER OBD port

6E±25 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
General Service Information
Serviceability Issues
Non-OEM Parts
All of the OBD diagnostics have been calibrated to run
with OEM parts. Accordingly, if commercially sold sensor
or switch is installed, it makes a wrong diagnosis and turn
on the MIL (ªCheck Engineº lamp).
Aftermarket electronics, such as cellular phones,
stereos, and anti-theft devices, may radiate EMI into the
control system if they are improperly installed. This may
cause a false sensor reading and turn on the MIL (ªCheck
Engineº lamp).
Poor Vehicle Maintenance
The sensitivity of OBD diagnostics will cause the MIL
(ªCheck Engineº lamp) to turn on if the vehicle is not
maintained properly. Restricted oil filters, fuel filters, and
crankcase deposits due to lack of oil changes or improper
oil viscosity can trigger actual vehicle faults that were not
previously monitored prior to OBD. Poor vehicle
maintenance can not be classified as a ªnon-vehicle
faultº, but with the sensitivity of OBD diagnostics, vehicle
maintenance schedules must be more closely followed.
Related System Faults
Many of the OBD system diagnostics will not run if the
ECM detects a fault on a related system or component.
Visual/Physical Engine Compartment
Inspection
Perform a careful visual and physical engine
compartment inspection when performing any diagnostic
procedure or diagnosing the cause of an emission test
failure. This can often lead to repairing a problem without
further steps. Use the following guidelines when
performing a visual/physical inspection:

Inspect all vacuum hoses for punches, cuts,
disconnects, and correct routing.

Inspect hoses that are difficult to see behind other
components.

Inspect all wires in the engine compartment for proper
connections, burned or chafed spots, pinched wires,
contact with sharp edges or contact with hot exhaust
manifolds or pipes.
Basic Knowledge of Tools Required
NOTE: Lack of basic knowledge of this powertrain when
performing diagnostic procedures could result in an
incorrect diagnosis or damage to powertrain
components. Do not attempt to diagnose a powertrain
problem without this basic knowledge.
A basic understanding of hand tools is necessary to effec-
tively use this section of the Service Manual.
Serial Data Communications
Class II Serial Data Communications
This vehicle utilizes the ªClass IIº communication system.
Each bit of information can have one of two lengths: longor short. This allows vehicle wiring to be reduced by
transmitting and receiving multiple signals over a single
wire. The messages carried on Class II data streams are
also prioritized. If two messages attempt to establish
communications on the data line at the same time, only
the message with higher priority will continue. The device
with the lower priority message must wait.
On this vehicle the Tech 2 displays the actual values for
vehicle parameters. It will not be necessary to perform
any conversions from coded values to actual values.
On-Board Diagnostic (OBD)
On-Board Diagnostic Tests
A diagnostic test is a series of steps, the result of which is
a pass or fail reported to the diagnostic executive. When
a diagnostic test reports a pass result, the diagnostic
executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The diagnostic test has passed during the current
ignition cycle.

The fault identified by the diagnostic test is not
currently active.
When a diagnostic test reports a fail result, the diagnostic
executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The fault identified by the diagnostic test is currently
active.

The fault has been active during this ignition cycle.

The operating conditions at the time of the failure.
Comprehensive Component Monitor
Diagnostic Operation
Comprehensive component monitoring diagnostics are
required to operate engine properly.
Input Components:
Input components are monitored for circuit continuity and
out-of-range values. This includes rationality checking.
Rationality checking refers to indicating a fault when the
signal from a sensor does not seem reasonable. Accel
Position (AP) sensor that indicates high throttle position
at low engine loads or MAP voltage. Input components
may include, but are not limited to the following sensors:

Intake Air Temperature (IAT) Sensor

Crankshaft Position (CKP) Sensor

Intake throttle Position (ITP) Sensor

Engine Coolant Temperature (ECT) Sensor

Camshaft Position (CMP) Sensor

Manifold absolute Pressure (MAP) Sensor

Accel Position Sensor

Fuel Temp Sensor

Rail Pressure Sensor

Oil Temp Sensor

EGR Pressure Sensor

Vehicle Speed Sensor

6E±27 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS

Non-Emissions related

Dose not request illumination of any lamp

Stores a History DTC on the
first trip with a fail

Stores Fail Record when test fails

Updates the Fail Record each time the diagnostic test
fails
Storing and Erasing Freeze Frame Data and Failure
Records
The data captured is called Freeze Frame data. The
Freeze Frame data is very similar to a single record of
operating conditions. Whenever the MIL is illuminated,
the corresponding record of operating conditions is
recorded to the Freeze Frame buffer.
Data from these faults take precedence over data
associated with any other fault. The Freeze Frame data
will not be erased unless the associated history DTC is
cleared.
Each time a diagnostic test reports a failure, the current
engine operating conditions are recorded in the
Failure
Records
buffer. A subsequent failure will update the
recorded operating conditions. The following operating
conditions for the diagnostic test which failed
typically
include the following parameters:

Engine Speed

Engine Load

Engine Coolant Temperature

Vehicle Speed

Intake Throttle Position

MAP

Injector Base Pulse Width

Loop Status
Data Link Connector (DLC)
The provision for communication with the contorl module
is the Data Link Connector (DLC). It is located at behind
the lower front instrument panel. The DLC is used to
connect to a Tech 2. Some common uses of the Tech 2
are listed below:

Identifying stored Diagnostic Trouble Codes (DTCs).

Clearing DTCs.

Performing out put control tests.

Reading serial data.
060RW046
Verifying Vehicle Repair
Verification of vehicle repair will be more comprehensive
for vehicles with OBD system diagnostic. Following a
repair, the technician should perform the following steps:
1. Review and record the Fail Records and/or Freeze
Frame data for the DTC which has been diagnosed.
2. Clear DTC(s).
3. Operate the vehicle within conditions noted in the Fail
Records and/or Freeze Frame data.
4. Monitor the DTC status information for the specific
DTC which has been diagnosed until the diagnostic
test associated with that DTC runs.
Following these steps are very important in verifying
repairs on OBD systems. Failure to follow these steps
could result in unnecessary repairs.
Reading Flash Diagnostic Trouble Codes
The provision for communicating with the Engine Control
Module (ECM) is the Data Link Connector (DLC). The
DLC is located in the front console box. It is used in the
assembly plant to receive information in checking that the
engine is operating properly before it leaves the plant.
The diagnostic trouble code(s) (DTCs) stored in the
ECM's memory can be read either through a hand-held
diagnostic scanner plugged into the DLC or by counting
the number of flashes of the ªCheck Engineº Malfunction
Indicator Lamp (MIL) when the diagnostic test terminal of
the DLC is grounded. The DLC terminal ª6º (diagnostic
request) is pulled ªLowº (grounded) by jumpering to DLC
terminal ª4º, which is a ground wire.
This will signal the ECM that you want to ªflashº DTC(s), if
any are present. Once terminals ª4º and ª6º have been
connected, the ignition switch must be moved to the ªONº
position, with the engine not running.
The ªCheck EngineºMIL will indicate a DTC three times if
a DTC is present. If more than one DTC has been stored

6E±93 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Circuit Description
The rail pressure control valve (RPCV) is built in the high
pressure oil circuit.
RPCV is an important device which is used to control oil
pressure in the HEUI system.
The circuit receives current through Engine 15A fuse from
the battery, current flowing in the order of RPCV.
Action Taken When the DTC Sets

The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC

DTC P1196 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the ECM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at ECM ± Inspect harness connectors
for backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.

Damaged harness ± Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
Rail Pressure Control display on the Tech 2 while
moving connectors and wiring harnesses related to the
Rail Pressure Control. A change in the Rail Pressure
Control display will indicate the location of the fault.
If DTC P1196 cannot be duplicated, the information
included in the Failure Records data can be useful in
determining vehicle mileage since the DTC was last set.
If it is determined that the DTC occurs intermittently.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. Verifies that the fault is present.
DTC P1196 ± RP System High Warning

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Engine is running.
2. Observe the ªRail Pressure Controlº display on the
Tech 2.
Is the action correct?
ÐGo to Step 4Go to Step 3
3Replace the RPCV.
Is the action complete?
ÐVerify repairGo to Step 4
41. Engine is running.
2. Review and record Tech 2 Failure Records data.
3. Operate the vehicle within Failure Records
conditions as noted.
4. Using a Tech 2, monitor ª DTCº info for DTC P1196.
Does the Tech 2 indicate DTC P1196 failed this
ignition?
ÐGo to Step 5Ð
51. Check the 2 way valve.
2. Observe the ªRP Controlº display on the Tech 2.
Is the action correct?
ÐGo to Step 4Go to Step 6
6Replace the 2 way valve.
Is the action complete?
ÐVerify repairÐ

6E±176
4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Symptom Diagnosis
Preliminary Checks
Before using this section, perform the ªOn±Board
Diagnostic (OBD) System Checkº and verify all of the
following items:

The powertrain control module (ECM) and
malfunction indicator lamp (MIL) (CHECK ENGINE
lamp) are operating correctly.

There are no DTC(s) stored.

Tech±2 data is within normal operating range. Refer
to
Typical Scan Data Values.

Verify the customer complaint and locate the correct
symptom in the table of contents. Perform the
procedure included in the symptom chart.
Visual/Physical Check
Several of the symptom procedures call for a careful
visual/physical check. This can lead to correcting a
problem without further checks and can save valuable
time.
This check should include the following items:

ECM grounds for cleanliness, tightness and proper
location.

Vacuum hoses for splits, kinks, and proper
connections, as shown on the ªVehicle Emission
Control Informationº label. Check thoroughly for any
type of leak or restriction.

Air intake ducts for collapsed or damaged areas.

Injector wires for cracking, hardness, and carbon
tracking.

Wiring for proper connections, pinches and cuts.
Intermittents
IMPORTANT:An intermittent problem may or may not
turn on the malfunction indicator lamp (MIL) or store a
DTC. DO NOT use the Diagnostic Trouble Code (DTC)
charts for intermittent problems. The fault must be
present to locate the problem.
Most intermittent problems are caused by faulty electrical
connections or wiring. Perform a careful visual/physical
check for the following conditions:

Poor mating of the connector halves or a terminal not
fully seated in the connector (backed out).

Improperly formed or damaged terminal.

All connector terminals in the problem circuit should
be carefully checked for proper contact tension.

Poor terminal±to±wire connection. This requires
removing the terminal from the connector body to
check.
Road test the vehicle with a Digital Multimeter
(5-8840-0285-0) connected to a suspected circuit. An
abnormal voltage when the malfunction occurs is a good
indication that there is a fault in the circuit being
monitored.
Use a scan tool to help detect intermittent conditions. The
scan tools have several features that can be used to
locate an intermittent condition. Use the following feature
to find intermittent faults:
Using a Tech±2 ªFreeze Frameº buffer or ªFailure
Recordsº buffer can aid in locating an intermittent
condition. Review and record the information in the
freeze frame or failure record associated with the
intermittent DTC being diagnosed. The vehicle can
be driven within the conditions that were present
when the DTC originally set.
To check for loss of diagnostic code memory, disconnect
the MAP sensor and idle the engine until the MIL (CHECK
ENGINE lamp) comes on. DTC P0107 should be stored
and kept in memory when the ignition is turned ªOFF.º If
not, the ECM is faulty. When this test is completed, make
sure that you clear the DTC P0107 from memory.
An intermittent MIL (CHECK ENGINE lamp) with no
stored DTC may be caused by the following:

MIL (CHECK ENGINE lamp) wire to ECM shorted to
ground.

Poor ECM grounds. Refer to the ECM wiring
diagrams.
Check for improper installation of electrical options such
as lights, cellular phones, etc.
Check for an open diode across the A/C compressor
clutch and check for other open diodes (refer to wiring
diagrams in
Electrical Diagnosis).
If problem has not been found, refer to
ECM Connector
Symptom
tables.

6E±177 4JX1±TC ENGINE DRIVEABILITY AND EMISSIONS
Hard Start Symptom

StepActionValue(s)Ye sNo
1DEFINITION:
Engine cranks, but does not start for a long time. Does
eventually run, or may start but immediately stalls.
Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found,
correct the condition as instructed in the bulletin.
Was a bulletin found that addresses the symptom?
ÐVerify repairGo to Step 3
3Was a visual/physical check performed?
ÐGo to Step 4
Go to
Visual/Physic
al Check
4Check engine coolant temperature (ECT) sensor for
shift in value. After 8 hours with the hood up and the
engine not running, connect the scan tool. With the
ignition ªONº and the engine not running, compare
engine coolant temperature to manifold air
temperature.
Are ECT and MAT within the specified value of each
other?
+ 5
C (+ 9
F)Go to Step 8Go to Step 5
51. Using Tech±2, display the engine coolant
temperature and note the value.
2. Check the resistance of the engine coolant
temperature sensor.
3. Refer to
Engine Coolant Temperature Sensor
Temperature vs. Resistance
chart on DTC P0118
Diagnostic Support
for resistance specifications.
Is the resistance value near the resistance for the
temperature noted?
ÐGo to Step 7Go to Step 6
6Replace the ECT sensor.
Is the action complete?
ÐVerify repairÐ
7Locate and repair high resistance or poor connection in
the ECT signal circuit or the ECT sensor ground.
Is the action complete?
ÐVerify repairÐ
81. Injector Test
Operate the each injector by Tech 2 with the
ignition ªONº and check if the working noise
confirm.
2. If a problem is found, check the harness or replace
the injector.
Is the action complete?
ÐVerify repairGo to Step 9
9Check the oil rail pressure by Tech 2 at the cranking.
Is the pressure near the specified value?Less than 3
MPa
Go to Step 10Go to Step 11
10Check the oil leakage on the high oil pressure line.
If the oil leakage is found, repair as necessary.
Was the oil leakage found?
ÐVerify repairGo to Step 11
111. Check for water-or alcohol-contaminated fuel.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 12

7A±11 AUTOMATIC TRANSMISSION (4L30±E)
Fluid Condition
FLUID CONDITION
NORMAL*CONTAMINATED
COLORRED OR LIGHT
BROWNBROWNNON±TRANSPAR-
ENT / PINKBROWN
DRAIN RE-
QUIRED?NOYESYESYES
CONTAMINA±
TIONNONEVery small amount of
foreign material in bot-
tom of panContamination by cool-
ant or other sourceLarge pieces of metal
or other foreign materi-
al in bottom of pan
CORRECT
LEVEL AND
CONDITION
1. LOW LEVEL:
A. Add fluid to
obtain proper
level & check for
external leaks.
B. Correct cause of
leak.
2. HIGH LEVEL:
± Remove excess
fluid± Remove both pans
± Change filter
± Flush cooler
± Add new fluid
± Check level± Repair/replace
radiator cooler
± Transmission
overhaul required
± Check for:

Damaged plates
and seals

Contaminated
solenoids
± Flush cooler
± Add new fluid
± Check level± Transmission
overhaul required
± Flush cooler and
cooler lines
± Add new fluid
± Check level
*Fluid should be changed according to maintenance
schedule.
Test Driving
Some 4L30±E automatic transmission complaint will
require a test drive as a part of the diagnostic procedure.
Some codes will not set unless the vehicle is moving. The
purpose of the test drive is to duplicate the customer's
complaint condition and set a current Powertrain Control
Module (PCM) trouble code. Perform this procedure
before each 4L30±E automatic transmission repair, and
again after repairs are made.
IMPORTANT:

Duplicate the condition under which the customer's
complaint was observed.

Depending on the complaint, the line pressure gauge
and the scan tool may be required during the test
drive.

During the test drive, it is important to record all
necessary data from the areas being monitored, for
use in diagnosis. Also listen for and note any unusual
noises.
The following procedure should be used to test drive
4L30±E automatic transmission complaint vehicles:
1. Turn the ignition ON without starting the engine.
Check that the ªCHECK TRANSº lamp comes on for
approximately 2 to 3 seconds and then goes out and
remains out.

If the lamp is flashing, GOTO Check Trans Indicator
in Transmission Control System (4L30±E) section.

If no serial data is present, GOTO OBD System
Check. Refer to Driveability and Emissions in
Engine section.
If the lamp stays ON or stays OFF, GOTO ªCheck
Transº Check in Transmission Control System
(4L30±E) section.
2. Drive the vehicle. During the test drive, be sure that
the transmission achieves normal operating
temperature (approx. 20 minutes).
Allow the transmission to go through all of its gear
ranges, checking shift timing and firmness. Duplicate
the owner's complaint condition as closely as
possible during the test drive.
3. If, during the test drive, the ªCHECK TRANSº lamp
comes on, use the scan tool to check for trouble
codes.
4. If, during the test drive, a problem is felt, but the
ªCHECK TRANSº lamp does not come on and no
trouble codes are present, drive the vehicle with the
PCM disconnected (manually shifting the vehicle).

In Manual L, the vehicle operates in first gear.

In Manual 2, the vehicle operates in third gear.

In Manual 3 or ªDº, the vehicle operates in fourth
gear.
If the problem still exists with the PCM disconnected,
refer to Mechanical/Hydraulic Diagnosis in this
section.
5. If no problem has been found at this point, check all
underhood connections that supply power to the PCM
and ignition fuses. Physically and visually inspect all
the PCM harness connectors for loose or corroded
terminals. Inspect the PCM ground points.

TRANSMISSION CONTROL SYSTEM (4L30±E)7A1±11
Diagnosis
Electronic Diagnosis
How To Diagnose The Problem
1. To avoid incorrect diagnostics, this book needs to be
followed accurately. Unless stated, do not jump
directly to a section that could contain the solution.
Some important information may be missed.
2. The sections in CAPITALS and bold are the main
sections that can be found in the contents.
3. The GOTO ªSECTIONº means to continue to check
going to the ªsectionº.
4. The GOTHROUGH ªSECTIONº means to go
through the ªsectionº and then to go back to the place
the GOTHROUGH was written.
5. BASIC ELECTRIC CIRCUITS:
You should understand the basic theory of electricity.
This includes the meaning of voltage, amps, ohms,
and what happens in a circuit with an open or shorted
wire. You should also be able to read and understand
wiring diagrams.
Check Trans Indicator
Find CHECK TRANS indicator and verify if it is
A. Flashing: GOTO DIAGNOSTIC CHECK.
B. Staying on: GOTHROUGH CHECK TRANS
CHECK.
C. Is never ON when the ignition key is turned on:
GOTHROUGH CHECK TRANS CHECK
D. Is ON during 2 to 3 seconds at ignition but OFF after:
Normal operation. No DTC or malfunction.
821RW261
Diagnostic Check
This test determines if the transmission or its inputs,
outputs, connections, or sensors are failing.
1. Connect the Tech2: GOTHROUGH Tech2 OBD II
CONNECTION.
2. Turn on the ignition but not the engine.3. Push ªF2º on Tech2 to see the Diagnostic Trouble
Code (DTC):
4. Do you have a DTC?
YES: write down all code numbers and do the DTC
CHECK
NO: the DTC can not help you finding the problem.
1. GOTHROUGH ªCHECK TRANSº CHECK
2. IF it is flashing and the flash is 0.2 seconds ON
and 0.2 seconds OFF, this means that you should
have a DTC stored. Please recheck GOTO
DIAGNOSTIC CHECK and if you find the same
problem, replace the Powertrain Control Module
(PCM).
Normal
C07RW047
Abnormal
C07RW048

7A1±20
TRANSMISSION CONTROL SYSTEM (4L30±E)
821RW263
810RT022
PIN 1 ± (Not used)
PIN 2 ± J1850 Bus + L line on 2±wire systems, or
single wire (Class 2)
PIN 3 ± (Not used)
PIN 4 ± Chassis ground pin
PIN 5 ± Signal ground pin
PIN 6 ± PCM diagnostic enable
PIN 7 ± (Not used)
PIN 8 ± (Not used)
PIN 9 ± Primary UART
PIN 10 ± (Not used)
PIN 11 ± (Not used)
PIN 12 ± ABS diagnostic or CCM diagnostic enable
PIN 13 ± SIR diagnostic enable
PIN 14 ± (Not used)
PIN 15 ± (Not used)
PIN 16 ± Battery power from vehicle unswitched (4
AMP MAX.)
Malfunction Indicator Lamp (MIL)
The Malfunction Indicator Lamp (MIL) looks the same as
the MIL you are already familiar with (ªCHECK ENGINEº
lamp). However, OBD II requires that it illuminate under a
strict set of guidelines. Basically, the MIL is turned on
when the PCM detects a DTC that will impact the vehicle's
emissions.
The MIL is under the control of the Diagnostic Executive.
The MIL will be turned on if a component or system which
has an impact on vehicle emissions indicates a
malfunction or fails to pass an emissions±related
diagnostic test. It will stay on until the system or
component passes the same test, for three consecutive
trips, with no emissions±related faults.
Types Of Diagnostic Trouble Codes (DTCs)
The Diagnostic Executive classifies Diagnostic Trouble
Codes (DTCs) into certain categories. Each type has
different requirements to set the code, and the Diagnostic
Executive will only illuminate the Malfunction Indicator
Lamp (MIL) for emissions±related DTCs. DTCs fall into
four categories: A, B, C, and D; only types A and B are
emission±related The following descriptions define these
categories:
TYPE A
Will store the DTC and turn on the MIL (ªCheck Engineº
lamp) on the first trip in which an emission±related
diagnostic test has run and reported a ªtest failedº to the
Diagnostic Executive.
TYPE B
Will store the DTC and turn on the MIL on the second
consecutive trip in which an emission±related diagnostic
test has run and reported a ªtest failedº to the Diagnostic
Executive. After one failure, the type B DTC is ªarmed,º
or prepared to store a history code and turn on the MIL if
a second failure occurs. One passed test will disarm a
type B DTC. Some special conditions apply to misfire and
fuel trim DTCs. For a type B DTC to store and turn on the
MIL, two ignition cycles are required.
TYPE C
Will store the DTC and turn on a ªSERVICEº lamp
(ªCheck Transº lamp) on the first trip that a
non±emission±related diagnostic test has run and
reported a ªtest failedº to the Diagnostic Executive. This
type of DTC will be used in future applications.
TYPE D
Will store a DTC but will not turn on the MIL on the first
trip that a non±emission±related diagnostic test has run
and reported a ªtest failedº to the Diagnostic Executive.
These codes can be very helpful for vehicle service when
the driver may comment about a condition, but the MIL did
not turn on.
Clear DTC
NOTE: If you clear the DTC (Diagnostic Trouble Codes)
you will not be able to read any codes recorded during the
last occurrence.