1998 ISUZU TROOPER check engine

6E±41 ENGINE DRIVEABILITY AND EMISSIONS
If the MIL was set by either a fuel trim or misfire-related
DTC, additional requirements must be met. In addition to
the requirements stated in the previous paragraph, these
requirements are as follows:

The diagnostic tests that are passed must occur with
375 RPM of the RPM data stored at the time the last
test failed.

Plus or minus ten (10) percent of the engine load that
was stored at the time the last failed.

Similar engine temperature conditions (warmed up or
warming up ) as those stored at the time the last test
failed.
Meeting these requirements ensures that the fault which
turned on the MIL has been corrected.
The MIL (ªCheck Engineº lamp) is on the instrument
panel and has the following function:

It informs the driver that a fault affects vehicle emission
levels has occurred and that the vehicle should be
taken for service as soon as possible.

As a bulb and system check, the MIL will come ªONº
with the key ªONº and the engine not running. When
the engine is started, the MIL will turn ªOFF.º

When the MIL remains ªONº while the engine is
running, or when a malfunction is suspected due to a
driveability or emissions problem, a Powertrain
On-Board Diagnostic (OBD ll) System Check must be
performed. The procedures for these checks are given
in On-Board Diagnostic (OBD) System Check. These
checks will expose faults which may not be detected if
other diagnostics are performed first.
DTC Types
Each DTC is directly related to a diagnostic test. The
Diagnostic Management System sets DTC based on the
failure of the tests during a trip or trips. Certain tests must
fail two (2) consecutive trips before the DTC is set. The
following are the four (4) types of DTCs and the
characteristics of those codes:

Type A

Emissions related

Requests illumination of the MIL of the first trip with a
fail

Stores a History DTC on the first trip with a fail

Stores a Freeze Frame (if empty)

Stores a Fail Record

Updates the Fail Record each time the diagnostic
test fails

Type B

Emissions related

ªArmedº after one (1) trip with a fail

ªDisarmedº after one (1) trip with a pass

Requests illumination of the MIL on the
second
consecutive trip
with a fail

Stores a History DTC on the second consecutive trip
with a fail (The DTC will be armed after the first fail)

Stores a Freeze Frame on the second consecutive
trip with a fail (if empty)
Stores a Fail Record when the first test fails (not
dependent on
consecutive trip fails)

Updates the Fail Record each time the diagnostic
test fails

Type C (if the vehicle is so equipped)

Non-Emissions related

Requests illumination of the Service Lamp or the
service message on the Drive Information Center
(DIC) on the
first trip with a fail

Stores a History DTC on the
first trip with a fail


Does not store a Freeze Frame

Stores Fail Record when test fails

Updates the Fail Record each time the diagnostic
test fails

Type D (
Type D non-emissions related are not utilized
on certain vehicle applications).

Non-Emissions related

Dose not request illumination of any lamp

Stores a History DTC on the
first trip with a fail


Does not store a Freeze Frame

Stores Fail Record when test fails

Updates the Fail Record each time the diagnostic
test fails
IMPORTANT:Only four Fail Records can be stored.
Each Fail Record is for a different DTC. It is possible that
there will not be Fail Records for every DTC if multiple
DTCs are set.
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:

Air Fuel Ratio

Air Flow Rate

Fuel Trim

Engine Speed

Engine Load

Engine Coolant Temperature

Vehicle Speed

TP Angle

MAP/BARO

Injector Base Pulse Width

Loop Status

6E±42
ENGINE DRIVEABILITY AND EMISSIONS
Intermittent Malfunction Indicator Lamp
In the case of an ªintermittentº fault, the MIL (ªCheck
Engineº lamp) may illuminate and then (after three trips)
go ªOFFº. However, the corresponding diagnostic trouble
code will be stored in the memory. When unexpected
diagnostic trouble codes appear, check for an intermittent
malfunction.
A diagnostic trouble code may reset. Consult the
ªDiagnostic Aidsº associated with the diagnostic trouble
code. A physical inspection of the applicable sub-system
most often will resolve the problem.
Data Link Connector (DLC)
The provision for communication with the control module
is the Data Link Connector (DLC). The DLC is used to
connect to Tech 2. Some common uses of Tech 2 are
listed below:

Identifying stored Diagnostic Trouble Codes (DTCs).

Clearing DTCs.

Performing output control tests.

Reading serial data.
TS24064
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
(Freeze Frame data will only be stored for an A or B
type diagnostic and only if the MIL has been
requested).
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 Diagnostic Trouble Codes Using
A Tech 2
The procedure for reading diagnostic trouble code(s) is to
used a diagnostic Tech 2. When reading DTC(s), follow
instructions supplied by Tech 2 manufacturer.
Clearing Diagnostic Trouble Codes
IMPORTANT:Do not clear DTCs unless directed to do
so by the service information provided for each diagnostic
procedure. When DTCs are cleared, the Freeze Frame
and Failure Record data which may help diagnose an
intermittent fault will also be erased from memory.
If the fault that caused the DTC to be stored into memory
has been corrected, the Diagnostic Executive will begin to
count the ªwarm-upº cycles with no further faults
detected, the DTC will automatically be cleared from the
PCM memory.
To clear Diagnostic Trouble Codes (DTCs), use the
diagnostic Tech 2 ªclear DTCsº. When clearing DTCs
follow instructions supplied by the tool manufacturer.
When Tech 2 is not available, DTCs can also be cleared
by disconnecting
one of the following sources for at least
thirty (30) seconds.
NOTE: To prevent system damage, the ignition key must
be ªOFFº when disconnecting or reconnecting battery
power.

The power source to the control module. Examples:
fuse, pigtail at battery PCM connectors etc.

The negative battery cable. (Disconnecting the
negative battery cable will result in the loss of other
on-board memory data, such as preset radio tuning).

6E±46
ENGINE DRIVEABILITY AND EMISSIONS
060RW223
The following is a brief description of each of the sub
menus in DTC Info and Specific DTC. The order in which
they appear here is alphabetical and not necessarily the
way they will appear on the Tech 2.
DTC Information Mode
Use the DTC info mode to search for a specific type of
stored DTC information. There are seven choices. The
service manual may instruct the technician to test for
DTCs in a certain manner. Always follow published
service procedures.
To get a complete description of any status, press the
ªEnterº key before pressing the desired F-key. For
example, pressing ªEnterº then an F-key will display a
definition of the abbreviated Tech 2 status.
060RW221
DTC Status
This selection will display any DTCs that have not run
during the current ignition cycle or have reported a test
failure during this ignition up to a maximum of 33 DTCs.
DTC tests which run and pass will cause that DTC
number to be removed from Tech 2 screen.Fail This Ignition
This selection will display all DTCs that have failed during
the present ignition cycle.
History
This selection will display only DTCs that are stored in the
PCM's history memory. It will not display Type B DTCs
that have not requested the MIL (ªCheck Engineº lamp). It
will display all type A and B DTCs that have requested the
MIL and have failed within the last 40 warm-up cycles. In
addition, it will display all type C and type D DTCs that
have failed within the last 40 warm-up cycles.
Last Test Failed
This selection will display only DTCs that have failed the
last time the test ran. The last test may have run during a
previous ignition cycle if a type A or type B DTC is
displayed. For type C and type D DTCs, the last failure
must have occurred during the current ignition cycle to
appear as Last Test Fail.
MILSVC or Message Requested
This selection will display only DTCs that are requesting
the MIL. Type C and type D DTCs cannot be displayed
using this option. This selection will report type B DTCs
only after the MIL has been requested.
Not Run Since Code Clear
This option will display up to 33 DTCs that have not run
since the DTCs were last cleared. Since any displayed
DTCs have not run, their condition (passing or failing) is
unknown.
Test Failed Since Code Clear
This selection will display all active and history DTCs that
have reported a test failure since the last time DTCs were
cleared. DTCs that last failed more than 40 warm-up
cycles before this option is selected will not be displayed.
Injector Balance Test
This test is conducted to make it sure that appropriate
electric signals are being sent to injectors Nos. 1±6.
Tech 2 must be used for this test.
Test Procedure:
1. Connect Tech 2 to the vehicle DLC.
2. Run the Engine at idle.

6E±47 ENGINE DRIVEABILITY AND EMISSIONS
3. Select F3: Miscellaneous Test in the Application
Menu.
060RW228
4. Select F7: Injector Balance Test in the Miscellaneous
Test.
060RX006
5. Select injector number and push ªinjector offº of soft
key.
060RW230
6. Make sure of engine speed change.
7. In the engine speed whose change has been
confirmed, the injector electric circuit can be regard
as normal.
As for the engine speed whose change has not been
confirmed, the injector electric circuit or the injector
proper is faulty.
EGR Control Test
This test is conducted check EGR valve for its working.
Tech 2 must be used for this test.
Test Procedure:
1. Connect Tech 2 to the vehicle DLC.
2. Run the Engine at idle.
3. Select F3: Miscellaneous Test in the Application
Menu.
060RW228

6E±48
ENGINE DRIVEABILITY AND EMISSIONS
4. Select F5: EGR Control Test in the Miscellaneous
Test.
060RX008
5. Instruct EGR Valve to check a data list.
060RW234
6. If change in the data list shows a normal valve.
Idle Air Control System Test
This test is conducted check IAC system for its working.
Tech 2 must be used for this test.
Test Procedure:
1. Connect Tech 2 to the vehicle DLC.
2. Run the Engine at idle.3. Select F3: Miscellaneous Test in the Application
Menu.
060RW228
4. Select F3: IAC System Test in the Miscellaneous
Test.
060RX007

6E±49 ENGINE DRIVEABILITY AND EMISSIONS
5. Select F1: IAC Control Test.
060RW235
6. Instruct IAC system to check a data list.
060RW233

F0: RPM Control
060RW232

F2: IAC Reset
060RW231
7. If change in the data list shows a normal IAC.

6E±51 ENGINE DRIVEABILITY AND EMISSIONS
On-Board Diagnostic (OBD) System Check
TS321119
Circuit Description
The on-board diagnostic system check is the starting
point for any driveability complaint diagnosis. Before
using this procedure, perform a careful visual/physical
check of the PCM and engine grounds for cleanliness and
tightness.
The on-board diagnostic system check is an organized
approach to identifying a problem created by an
electronic engine control system malfunction.
Diagnostic Aids
An intermittent may be caused by a poor connection,
rubbed-through wire insulation or a wire broken inside the
insulation. Check for poor connections or a damaged
harness. Inspect the PCM harness and connector for
improper mating, broken locks, improperly formed or
damaged terminals, poor terminal-to-wire connection,
and damaged harness.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
1. The MIL (ªCheck Engineº lamp) should be ªONº
steady with the ignition ªONº/engine ªOFF.º If not,
Chart A-1 should be used to isolate the malfunction.
2. Checks the Class 2 data circuit and ensures that the
PCM is able to transmit serial data.
3. This test ensures that the PCM is capable of
controlling the MIL (ªCheck Engineº lamp) and the
MIL (ªCheck Engineº lamp) driver circuit is not
shorted to ground.
4. If the engine will not start, the
Cranks But Will Not
Run
chart should be used to diagnose the condition.
7. A Tech 2 parameter which is not within the typical
range may help to isolate the area which is causing
the problem.

6E±53 ENGINE DRIVEABILITY AND EMISSIONS
On-Board Diagnostic (OBD) System Check

StepActionValue(s)Ye sNo
11. Ignition ªON,º engine ªOFF.º
2. Observe the malfunction indicator lamp (MIL or
ªCheck Engineº lamp).
Is the MIL (ªCheck Engineº lamp)ªON?º
ÐGo to Step 2
Go to No MIL
(ªCheck
Engineº lamp)
21. Ignition ªOFF.º
2. Install a Tech 2.
3. Ignition ªON.º
4. Attempt to display PCM engine data with the Tech 2.
Does the Tech 2 display PCM data?
ÐGo to Step 3Go to Step 8
31. Using the Tech 2 output tests function, select MIL
(ªCheck Engineº lamp) dash lamp control and
command the MIL (ªCheck Engineº lamp) ªOFF.º
2. Observe the MIL (ªCheck Engineº lamp).
Did the MIL (ªCheck Engineº lamp) turn ªOFF?º
ÐGo to Step 4
Go to MIL
(ªCheck
Engineº lamp)
On Steady
4Attempt to start the engine.
Did the engine start and continue to run?
ÐGo to Step 5
Go to Cranks
But Will Not
Run
5Select ªDisplay DTCsº with the Tech 2.
Are any DTCs stored?
ÐGo to Step 6Go to Step 7
6Are two or more of the following DTCs stored? P0107,
P0108, P0113, P0118, P0122, P0123, P0712.?
Ð
Go to
ªMultiple
PCM
Information
Sensor DTCs
Setº
Go to
applicable
DTC table
7Compare PCM data values displayed on the Tech 2 to
the typical engine scan data values.
Are the displayed values normal or close to the typical
values?
Ð
Refer
to
Typical
scan data
value
Refer to
indicated
Component
System
Checks
81. Ignition ªOFF,º disconnect the PCM.
2. Ignition ªON,º engine ªOFF.º
3. Check the Class 2 data circuit for an open, short to
ground, or short to voltage. Also, check the DLC
ignition feed circuit for an open or short to ground
and the DLC ground circuit for an open.
4. If a problem is found, repair as necessary.
Was a problem found?
ÐGo to Step 2Go to Step 9
9Attempt to display PCM data with the Tech 2.
Does the Tech 2 display PCM engine data?
ÐGo to Step 2Go to Step 10
10Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
Powertrain Control Module
(PCM) in On-Vehicle Service.
Is the action complete?ÐGo to Step 2Ð