ISUZU TROOPER 1995 Workshop Manual

THROTTLE ANGLE
Displays in percent the amount the throttle is
open.
HEATED OXYGEN SENSOR (H02S)
The reading will be read out in millivolts (mv) with
a range from 1 to 999 mv. If the reading is
consistently
below 350 (350 mv), the fuel system
is running
lean as seen by the Engine Control
Module
(ECM) and if the reading is consistently
above
550 (550 mv), the system is running rich.
VEHICLE SPEED SENSOR (VSS)
Displays vehicle speed, useful in checking
speedometer accuracy.
PROGRAMMABLE READ ONLY MEMORY
(PROM)
ID
In this position the last4 digits of the Mem-Cal part
number will be displayed.
REVOLUTION PER MINUTE (RPM)
Displays engine speed. Often useful if extra
reference pulses are suspected. A sudden high
revolution per minute indication while at a steady
throttle
would indicate electrical interference
(EMI) in the reference circuit. This interference is
usually caused by ECM wires too close to ignition
secondary wires
or an open electronic ignition
ground circuit.
MILE PER HOUR (MPH)
Displays vehicle speed. Useful in checking
speedometer accuracy.
ENGINE COOLANT TEMPERATURE (ECT)
Displays engine temperature in degress centi­
grade.
After engine is started the temperature
should rise steadily to about
85-95·c, then
stabilize
when the thermostat opens.
INTAKE AIR TEMPERATURE (IAT)
SENSOR
Displays temperature of the intake manifold air.
Should read close to ambient air temperature
when the engine is cold, and rise
as underhood
and engine temperature increases.
DRIVEABILITY AND EMISSIONS 6E2-15
MANIFOLD ABSOLUTE PRESSURE (MAP)
The Manifold Absolute Pressure (MAP) Sensor
produces a low signal voltage when MAP is low
(high vacuum) and a high voltage when the
pressure is high (low vacuum).
With the ignition on and the engine stopped, the
manifold absolute pressure is equal
to
atmospheric pressure and the signal voltage will
be high. This information is used by the ECM as an
indication of vehicle altitude and is referred to as
barometric pressure. Comparison of this
barometric pressure reading
with a known good
vehicle
with the same sensor is a good way to
check accuracy
of a "suspect" sensor. Readings
should be the same
±0.4 Volt.
MAP
Sensors have a colored plastic insert visible
in the connector cavity.
Sensors with the same
insert color are identical in calibration. The
harness electrical connector color should also be
the same
as the sensor insert color.
BAROMETRIC PRESSURE (BARO)
Displays the MAP reading before the engine was
started. This value
will vary depending on
Barometric Pressure and altitude.
EXHAUST GAS RECIRCULATION (EGR)
(ON/OFF)
The exhaust gas recirculation system uses a valve
controlled by vacuum to feed a small amount of
exhaust gas back into the intake manifold to
control formation
of NOx. Like all ECM outputs the
"Scan tool" only indicates that the ECM has
commanded the function and does
not indicate
that the function has
really happened.
SHORT TERM (S.T.) FUEL TRIM AND LONG
TERM (L.T.) FUEL TRIM
On Fuel Injected Engines, normal readings for
these positions are around 128. If higher, it
indicates that the ECM is adding fuel to the base
fuel calculation because the system is lean.
If the
numbers are below 128, the
ECM is taking out fuel
from the base calculation because the system is
rich. The
S.T. Fuel Trim is short term corrective
action while the
L.T. Fuel Trim portion (which is a
long term correction)
will only change if the
intergrator has seen a condition which lasts
for a
calibrated period
of time.

6E2-16 DRIVEABILITV AND EMISSIONS
LONG TERM (LT.) FUEL TRIM
There are from zero to seventeen different cells
which the Engine Control Module (ECM) learns at
depending on revolution per minute (rpm) and
manifold absolute pressure. This parameter
will
display what cell the ECM is using for the fuel
calculation at the time.
IDLE AIR CONTROL (lAC) COUNTS
This system is used to control engine idle speed to
the desired rpm, for different operating
conditions.
In this diagnostic test mode, the
numbers
will indicate what position the ECM
thinks the valve is in. The ECM moves the idle air
control in counts and these counts are displayed
on a
"Scan tool".
DESIRED REVOLUTION PER MINUTE
Indicates the rpm to which the ECM is trying to
control the idle.
AIR CONDITIONING (A/C) REQUEST
Displays the state of the Air Conditioning (A/C)
signal line to the ECM. Should read "YES"
whenever the A/C is requested.
AIR CONDITIONING {A/C) CLUTCH
Displays "ON" when the ECM has commanded
the
A/C Clutch "ON".
POWER STEERING PRESSURE (PSP)
SWITCH
Displays the state of switch. This reading may
vary
with the tool used and the type of switch
installed on the vehicle. The important thing is
that the reading changes state (switches) when
the steering is moved against the stops.
BA TTERV POSITIVE VOLTAGE
Displays the battery positive voltage detected at
the
ECM ignition input.
SPARK ADVANCE
This is a amount of total spark advance including
the base electronic ignition timing.
START UP ENGINE COOLANT
This parameter is the engine coolant temperature
at the
time the engine was started.
ENGINE SPEED (RPM)
RPM calculated during a crank mode, helpful in
diagnosing a NON-start condition.
FUEL TRIM ENABLE
This value is an indication when the Fuel Trim
Enable values are being updated within the ECM
program.
AIR/FUEL RATIO
This is the air to fuel ratio that is being
commanded to the injectors.
INDUCTION AIR CONTROL
The "Scan tool" will display the command being
given to the induction air control
plate system
solenoid.
SECTION B-DRIVEABILITY SYMPTOMS
Always start with Section "A" "On-Board Diagnostic
System Check" before proceeding to the driveability
symptoms.
Section "A" checks the ECM which may
cause the driveability problem. A definition
of each
symptom is included. This will then lead to the most
probable causes of the driveability problem.
SECTION C-COMPONENTS SYSTEMS
There are many component systems that are used to
control fuel and emissions. Section "C" introduces
each component system or control
with a general
description, diagnosis, and on-vehicle service.
Each
of the Section "C" diagnosis sections will contain
information on
how the "Scan tool" can be used for
diagnosing a particular component when a trouble
code has
not been set. (example: Section "C1" under
diagnosis
will explain how the "Scan tool" can be used
for diagnosis as well as what the normal readings
would be for the ECM Sensors.
•

DRIVEABILITY AND EMISSIONS 6E2-17
I OPERATING CONDITIONS READ I
I SYSTEMS CONTROLLED I
• Air Conditioning "On" or "Off" • Evaporative Emission Canister
• Engine Coolant Temperature Purge
• Crankshaft Position • Exhaust Gas Recirculation
• Exhaust Heated Oxygen Sensor • Ignition Control
• Electronic Ignition Reference • Fuel Control
• Crankshaft Position
ENGINE • Idle Air Control
• Engine Speed (RPM} CONTROL • Electric Fuel Pump
• Manifold Absolute Pressure (MAP)
MODULE • Air Conditioning
• Battery Positive Voltage (ECM) • Diagnostics
• Throttle Position Sensor • Malfunction Indicator Lamp
• Vehicle Speed Sensor • Diagnostic Test Terminal
• Fuel Pump Voltage • Data Output
• Power Steering Pressure • Transmission Control Module
• Intake Air Temperature • Knock Sensor (DOHC)
• Differential Pressure • Induction Air Control Plate System
• Knock Sensor (DOHC)
(DOHC)
• Exhaust Gas Recirculation Vacuum
• Air Conditioning High Side Pressure
Fig. 6E2-3
ENGINE CONTROL MODULE (ECM) AND
SENSORS
This Section describes the Engine Control Module
(ECM) and the information sensors in the system.
Figure (Fig. 6E2-3) shows the operating conditions
which the
ECM may read and the systems thatthe ECM
may control.
FUEL CONTROL SYSTEM
The ECM controls the air/fuel delivery to the combus­
tion chamber by
controlling the fuel flow through the
injector(s).
ELECTRIC FUEL PUMP (IN-TANK)
The in-tank fuel pump is controlled by the ECM. When
ignition is turned on, the
pump will run for 2 seconds,
then stop
unless the engine is cranking or running.
EVAPORATIVE EMISSION (EVAP) CONTROL
SYSTEM
This system has a canister which stores fuel vapor
from the fuel tank. The fuel vapor is removed from the
canister and consumed in the
normal combustion
process when the engine
is running.
IGNITION CONTROL (IC)
This system is controlled by the ECM which controls
spark advance (timing) and is used on all engines.
EXHAUST GAS RECIRCULATION (EGR)
The exhaust gas recirculation system uses ECM
controlled valve to feed a small amount of exhaust gas
back into the intake
manifold to control formation of
NOx.
AIR CONDITIONING (A/C) CLUTCH CONTROL
The ECM may control the air conditioning clutch on the
compressor
to improve idle quality.
POSITIVE CRANKCASE VENTILATION (PCV)
The PCV system passes crankcase vapors into the
intake
manifold. This system is not controlled by the
ECM and is used on all engines.

6E2-18 DRIVEABILITV AND EMISSIONS
TOOLS NEEDED TO SERVICE THE SVSJEM
The system requires a data link connector read-out (Scan) tool, tachometer, test light, ohmmeter, digital voltmeter
with 10 megohms impedance (J-39200), vacuum gage and jumper wires for diagnosis. A test light or voltmeter
must be used when specified in the procedures. They must NOT be interchanged. For more complete information
on the operation
of these tools, see the manufacturer's instructions.
Voltmeter
Voltage position measures amount of voltage when
connected in
parallel to an existing circuit. A digital
voltmeter
with 10 megohm input impedance is used
because this type
of meter will not load down the
circuit and
result in faulty readings. Some circuits
require accurate
low voltage readings, and some
circuits in the engine
control module have a very high
resistance.
Digital multimeter: J-39200 or equivalent
Fig. 6E2-4
Ammeter
When used as ammeter, this meter also accurately
measures extremely low current flow. Refer to meter
instructions
for more information.
• Selector must be set properly for both function
and range.
DC is used for most automotive
measurements.
Digital multimeter: J-39200 or equivalent
Ohmmeter
Measures resistance of circuit directly in ohms.
Refer to meter instructions
for more information.
• OL Display in all ranges indicates open circuit.
• Zero display in all ranges indicates a short circuit.
• Intermittent connection in circuit may be
indicated by digital reading that will not stabilize
on circuit.
• Range Switch
200 -Reads ohms
directly
2K, 20K, 200K -Reads ohms in thousands
2M and 20M -Reads ohms in
millions
Digital multimeter:
J-39200 or equivalent
Vacuum pump (20 in. hydragyrum minimum)
Use gage to monitor manifold engine vacuum and the
hand pump to check vacuum sensors,
solenoids and
valves.
Vacuum pump: J-23738
Fig. 6E2-5
Unpowered test light
Used to check wiring for complete circuit and short to
ground
or voltage.
Unpowered test light: J-34142-A
Fig. 6E2-6
•

Tachometer
Use inductive trigger signal pickup type to check
revolution per minute.
Fig. 6E2-7
Multiport fuel injection (MFI) diagnostic kit
Used to diagnose MFI systems.
The kit
includes:
• Fuel
Pressure Gage-to check fuel pump pressure
and compare injector pressure
drop for equal fuel
distribution.
• Injector Test Light-to check electrical circuit to an
injector.
• Injector Test-to energize each fuel injector for a
precise
amount of time to perform injector
balance test in CHART C-2A by checking each
injector's pressure
drop using pressure gage.
MFI test kit: J-34730-8
Fuel pressure gage
Used to check and monitor fuel line pressure of port
fuel system.
MFI test kit: J-34730-8
Injector test light
Used to check electrical circuit to a port fuel injector.
MFI test kit: J-34730-8
Injector tester
Used to energize each fuel injector for a precise
amount of time to perform injector balance test in
CHART C-2A by checking each injector's pressure drop
using pressure gage.
MFI test kit: J-34730-8
DRIVEABILITY AND EMISSIONS 6E2-19
Fig. 6E2-8
Spark tester
Use to check available secondary ignition voltage.
Also called
an ST125.
Spark
tester: J-26792
Fig. 6E2-9
Connector test adapter kit
Used to make electrical test connections in current
Weather Pack, Metri-Pack and Micro-Pack
style
terminals.
Terminal test adapter kit: J-35616
Fig. 6E2-10

6E2-20 DRIVEABILITV AND EMISSIONS
Circuit tester
Used to check all relays and solenoids before
connecting them to a
new engine control module.
Measures the circuit resistance and indicates pass or
fail via green or red LED. Amber LED indicates current
polarity. Can also be used as a non-powered continuity
checker.
Engine
control module circuit tester: J-34636
Fig.
6E2-11
Metri-pack terminal remover
Used to remove 150 series Metri-Pack "pull-to-seat"
terminals
from connectors.
Terminal remover: J-35689-A
Fig. 6E2-12
Idler air control (lAC) system driver
Used to test lAC motor for correct functioning and
proper response to commands.
lAC system driver: J-37027-A
Fig. 6E2-13
Weather pack terminal remover
Used to remove Terminals from Weather Pack
connectors.
Weather pack terminal remover: J-28742-A
Fig. 6E2-13
•

DRIVEABILITY AND EMISSIONS 6E2-21
Engine control module connector terminal remover Intake manifold diagnostic plate
Used to remove terminal from Micro-Pack connectors.
Engine
control module connector terminal remover: J-
33095
Used to fuel rail pressure test and fuel injector balance
test.
Fig. 6E2-14
Intake manifold diagnostic plate: J-39185
GROUND BOLT
€3 EXHAUST GAS RECIRCULATION (EGR) EXHAUST MANIFOLD PLATE
INTAKE BOLT SPACER
Fig. 6E2-14
GENERAL SPECIFICATIONS
"S''
Many of the specifications used in this section are located on the Vehicle Emission Control Information Label
under the hood.
Listed on the chart
below are locations of specifications used in this Section.
Specification Location of information
Engine Timing
Not adjustable, engine control module controls timing.
Idle Speed Not adjustable, engine control module controls idle.
Spark Plug Type See "Identification" in Section OA.
Spark Plug Gap Vehicle Emission Control Information Label.
Engine Diagnostic Trouble 8th digit of VIN number. See "Maintenance Service Data" in Section 08.
Code
Part Numbers of Major AIPDN (American lsuzu Parts Dept. Network)
Components
Replacement of Vehicle ISUZU Parts Catalog.
Emission Control
Information Label
AIPDN
(American lsuzu Parts Dept. Network)

6E2-22 DRIVEABILITV AND EMISSIONS
(DOHC)
(SOHC)
VACUUM HOSE ROUNTING DIAGRAM
EGR
INDUCTION-----­
AIR CONTROL
VALVE
BACK PRESSURE
TRANSDUCER
t
TO
THROTTLE
BODY
FUELPRESSURE ~
CONTROL ~ MAPSENSOR
VALVE (..._ _____ R_A_D _I A_T_O_R ____ ___.)
MAP
SENSOR
EGR------,
BACK PRESSURE
TRANSDUCER
FUEL
TANK
VACUUM
SWITCH
VALVE
CHECK&
RELIEF
c:::=::::::::::::::;:T=====!.J VALVE
L-~~~~~ ...J;::...u..-+----'~THROTTLE BODY
IGNITION
CONTROL
MODULE <==><==::>
[ RADIATOR )
~---------------------
VACUUM
SWITCH
VALVE
FUEL PRESSURE
CONTROL
VALVE
..

DRIVEABILITY AND EMISSIONS 6E2-23
SECTION A
ENGINE COMPONENTS/WIRING DIAGRAMS/DIAGNOSTIC
CHARTS
CONTENTS
On-Board Diagnostic (OBD} System Check . 6E2-23
Basic Procedure . . . . . . . . . . . . . . . . . . . . . 6E2-23
Engine Component Location . . . . . . . . . . 6E2-24
Engine Control Module Wiring
Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . 6E2-26
Engine Control Module (ECM) Connector
Identification . . . . . . . . . . . . . . . . . . . . . 6E2-33
"SCAN TOOL" On-Board Diagnostic (OBD)
System Check . . . . . . . . . . . . . . . . . . . . 6E2-34
On-Board Diagnostic (OBD} System Check . 6E2-36
Won't Flash Diagnostic Trouble Code
(DTC)
12 No "Check Engine" Malfunction
Indicator Lamp (MIL)-Chart A-1 . . . . . . 6E2-38
No Data Link Connector (DLC) Data or
Won't Flash Diagnostic Trouble Code
(DTC)
21 "Check Engine" Malfunction
Indicator Lamp (MIL} "On" Steady-
Chart A-2 . . . . . . . . . . . . . . . . . . . . . . . . . 6E2-40
Engine Crank But Will Not
Run-Chart A-3 . . . . . . . . . . . . . . . . . . . . . 6E2:.....42
Fuel Pump Relay Circuit-Chart A-5 . . . . . 6E2-48
Fuel System Pressure Test-Chart A-7 ..• /6E2-50
Intake Manifold Diagnostic Plate Chart/
A-8 ......................... ,-:· . . . 6E2-56
Diagnostic Trouble Code (DTC~13 /
Heated Oxygen Sensor (H02 Circuit
(Open Grounded Circuit) . . . . . . . . . . . 6E2-58
Diagnostic Trouble Code (D'JiC) 14A
Engine Coolant Temperaiure (ECT}
Sensor Circuit (High -:remperature
Indicated) ....... /. . . . . . . . . . . . . . . . 6E2-60
Diagnostic Trouble P'ode (DTC} 14B
Engine
Coolan·vremperature (ECT)
Sensor Circuit'(Low Temperature
Indicated) ./. . . . . . . . . . . . . . . . . . . . . . . 6E2-62
Diagnostic Jtouble Code (DTC) 21A
Throtti~,.Position (TP) Sensor
Circu)t (Signal Voltage High) . . . . . . . . 6E2-64
Diag.,Ostic Trouble Code (DTC) 21B
Jflrottle Position (TP} Sensor
//Circuit (Signal Voltage Low} ........ 6E2-66
ON-BOARD DIAGNOSTIC (OBD) SYSTEM
CHECK
The "On-Board Diagnostic System Check" verifies the
system is functioning correctly.
Some special
considerations
to keep in mind while making the "On­
Board Diagnostic System Check" are:
Diagnostic Trouble Code (DTC(23A
Intake Air Temperature (IAT)
Sensor Circuit (low Temperature
Indicated) ......................... 6E2-68
Diagnostic Trouble Code (DTC) 23B
Intake Air Temperature (IAT)
Sensor Circuit (High Temperature
Indicated) ... / ...................... 6E2-70
Diagnostic T[ouble Code (DTC} 24
Vehicle )!Peed Sensor (VSS} Circuit ... 6E2-72
DiagnostiC Trouble Code (DTC) 32
Exh,tist Gas Recirculation (EGR}
Cir,.Cuit ............................ 6E2-74
Dia,gnostic Trouble Code (DTC} 33A
·Manifold Absolute Pressure (MAP)
Sensor Circuit (Signal Voltage
High-Low Vacuum) ................. 6E2-76
Diagnostic Trouble Code (DTC) 33B
Manifold Absolute Pressure (MAP}
Sensor Circuit (Signal Voltage
Low-High Vacuum) ................. 6E2-78
Diagnostic Trouble Code (DTC) 42
Ignition Control (IC) Circuit . . . . . . . . . . 6E2-80
Diagnostic Trouble Code (DTC} 43
Knock Sensor (KS} Circuit (DOHC) .... 6E2-82
Diagnostic Trouble Code (DTC) 44
Heated Oxygen Sensor (H02S} Circuit
(Lean Heated Oxygen Sensor (H02S)
Signal Indicated} . . . . . . . . . . . . . . . . . . . 6E2-84
Diagnostic Trouble Code (DTC) 45
Heated Oxygen Sensor (H02S) Circuit
(Rich Heated Oxygen Sensor (H02S)
Signal Indicated) . . . . . . . . . . . . . . . . . . . 6E2-86
Diagnostic Trouble Code (DTC) 51
Engine Control Module (ECM} Failure
ECM Failed
or Electrically Erasable
Programmable Read Memory Only
Failure} ........................... 6E2-88
Blocking Drive Wheels
The vehicle drive wheels should always be
blocked
while checking the system.
BASIC PROCEDURE
If the basic information on using the diagnostic
procedures contained in this section has
not been
reviewed, refer
to the introduction of this section.

6E2-24 DRIVEABILITY AND EMISSIONS
ENGINE COMPONENT LOCATION (SOHC)
UNDERHOOD
FUSE/RELAY
CENTER
8 A
T
T
E
R y
0 COMPUTER HARNESS
C1 Engine control module (ECM) *
C2 DLC diagnostic connector
C3 "Check Engine" Malfunction
indicator lamp
C4 Engine harness connectors (3)
C5 ECM harness ground
C6 Fuse panel
C7 Electronic ignition ground
CS ECM main relay
C9 Fuel pump fuse 15A
C11 Oxygen 1 OA heater fuse
C12 30A ECM main fusible link
0 ECM CONTROLLED
COMPONENTS
1 Fuel injector
2 Idle air control
3 Fuel pump relay
6 Ignition control module
6a Ignition coils
12 Exhaust gas recirculation
(EGR) VSV
13 Air conditioning relay
14 Evaporate emission canister
purge VSV
Fig. 6E2-15
Q ECM INFORMATION
SENSORS
®
A Manifold Absolute Pressure
B Heated oxygen sensor
C Throttle position sensor
D Engine
coolant temperature
E Intake air temperature -
sensor
F Vehicle speed sensor
K Power steering pressure
switch (in-line)
@ EGRVALVE
@CHASSIS GROUNDS
* The ECM is located behind the
console in the lower dash.
®
[::::J EMISSION COMPONENTS
(NOT
ECM CONTROLLED)
N1 Crankcase vent valve (PCV)
N2 EGR valve back pressure
transducer
N3 Spark plugs
N4 Fuel rail test fitting (for fuel
pressure test)
N5 Crankshaft position sensor
N15 Fuel vapor canister