1998 ISUZU TROOPER Service Repair Manual

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Page 1161 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±44
ENGINE DRIVEABILITY AND EMISSIONS
Getting Started
Before operating the Isuzu PCMCIA card with the Tech
2, the following steps must be performed:
1. The Isuzu 98 System PCMCIA card (1) inserts

Page 1162 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±45 ENGINE DRIVEABILITY AND EMISSIONS
060RW218
Menu
The following table shows, which functions are used
the available equipment versions.
060RW228
DTC Modes
060RW229
On OBD passenger cars there ar

Page 1163 of 3573

ISUZU TROOPER 1998 Service Repair Manual 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 n

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.

Page 1164 of 3573

ISUZU TROOPER 1998 Service Repair Manual 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 n

Page 1165 of 3573

ISUZU TROOPER 1998 Service Repair Manual 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 n

Page 1166 of 3573

ISUZU TROOPER 1998 Service Repair Manual 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 i

Page 1167 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±50
ENGINE DRIVEABILITY AND EMISSIONS
Primary System-Based Diagnostic
Primary System-Based Diagnostic
There are primary system-based diagnostics which
evaluate system operation and its effect on ve

6E±50
ENGINE DRIVEABILITY AND EMISSIONS
Primary System-Based Diagnostic
Primary System-Based Diagnostic
There are primary system-based diagnostics which
evaluate system operation and its effect on vehicle
emissions. The primary system-based diagnostics are
listed below with a brief description of the diagnostic
function:
Oxygen Sensor Diagnosis
The fuel control heated oxygen sensors (Bank 1 HO2S 1
and Bank 2 HO2S 1) are diagnosed for the following
conditions:
Inactive signal (output steady at bias voltage ± approx.
450 mV)
Signal fixed high
Signal fixed low
If the oxygen sensor pigtail wiring, connector or terminal
are damaged, the entire oxygen sensor assembly must
be replaced. DO NOT attempt to repair the wiring,
connector or terminals. In order for the sensor to function
properly, it must have clean reference air provided to it.
This clean air reference is obtained by way of the oxygen
sensor wire(s). Any attempt to repair the wires, connector
or terminals could result in the obstruction of the
reference air and degrade oxygen sensor performance.
Refer to
On-Vehicle Service, Heated Oxygen Sensors.
Fuel Control Heated Oxygen Sensor
The main function of the fuel control heated oxygen
sensors is to provide the control module with exhaust
stream oxygen content information to allow proper fueling
and maintain emissions within mandated levels. After it
reaches operating temperature, the sensor will generate
a voltage, inversely proportional to the amount of oxygen
present in the exhaust gases. The control module uses
the signal voltage from the fuel control heated oxygen
sensors while in closed loop to adjust fuel injector pulse
width. While in closed loop, the PCM can adjust fuel
delivery to maintain an air/fuel ratio which allows the best
combination of emission control and driveability.
HO2S Heater
Heated oxygen sensors are used to minimize the amount
of time required for closed loop fuel control to begin
operation and to allow accurate catalyst monitoring. The
oxygen sensor heater greatly decreases the amount of
time required for fuel control sensors (Bank 1 HO2S 1 and
Bank2 HO2S 1) to become active. Oxygen sensor
heaters are required to maintain a sufficiently high
temperature which allows accurate exhaust oxygen
content readings further away from the engine.
Fuel Trim System Monitor Diagnostic
Operation
Fuel Trim System Monitor Diagnostic
Operation
This system monitors the averages of short-term and
long-term fuel trim values. If these fuel trim values stay at
their limits for a calibrated period of time, a malfunction is
indicated. The fuel trim diagnostic compares the
averages of short-term fuel trim values and long-term fuel
trim values to rich and lean thresholds. If either value is
within the thresholds, a pass is recorded. If both values
are outside their thresholds, a rich or lean DTC will be
recorded.
The fuel trim system diagnostic also conducts an intrusive
test. This test determines if a rich condition is being
caused by excessive fuel vapor from the EVAP canister.
In order to meet OBD requirements, the control module
uses weighted fuel trim cells to determine the need to set
a fuel trim DTC. A fuel trim DTC can only be set if fuel trim
counts in the weighted fuel trim cells exceed
specifications. This means that the vehicle could have a
fuel trim problem which is causing a problem under
certain conditions (i.e., engine idle high due to a small
vacuum leak or rough idle due to a large vacuum leak)
while it operates fine at other times. No fuel trim DTC
would set (although an engine idle speed DTC or HO2S
DTC may set). Use a Tech 2 to observe fuel trim counts
while the problem is occurring.
A fuel trim DTC may be triggered by a number of vehicle
faults. Make use of all information available (other DTCs
stored, rich or lean condition, etc.) when diagnosing a fuel
trim fault.
Fuel Trim Cell Diagnostic Weights
No fuel trim DTC will set regardless of the fuel trim counts
in cell 0 unless the fuel trim counts in the weighted cells
are also outside specifications. This means that the
vehicle could have a fuel trim problem which is causing a
problem under certain conditions (i.e. engine idle high due
to a small vacuum leak or rough due to a large vacuum
leak) while it operates fine at other times. No fuel trim
DTC would set (although an engine idle speed DTC or
HO2S DTC may set). Use a Tech 2 to observe fuel trim
counts while the problem is occurring.

Page 1168 of 3573

ISUZU TROOPER 1998 Service Repair Manual 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 d

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