language ISUZU TROOPER 1995 Workshop Manual

6E2-4 DRIVEABILITY AND EMISSIONS
BASIC KNOWLEDGE REQUIRED
Before using this section of the Service Manual,
there are some areas that you should be familiar
with. Without this basic knowledge, you will have
trouble using the diagnostic procedures
contained in this section.
BASIC ELECTRIC CIRCUITS
You should understand the basic theory of
electricity, and know the meaning of voltage,
amps, and ohms. You should understand what
happens in a circuit with an open or a shorted
wire. You
should be able to read and understand a
wiring diagram. A shortto ground is referred to as
a ground to distinguish it from a short between
wires.
USE OF CIRCUIT TESTING TOOLS
You should know how to use a test light, how to
connect and use a tachometer, and
how to use
jumper wires to by-pass components to test
circuits. Care
should be taken to not deform the
terminal when testing.
USE OF DIGITAL VOLT-OHM METER
(DVOM)
You should be familiar with the Digital Volt-Ohm
Meter, particularly special tool J-39200 or
equivalent. You should be able to measure
voltage, resistance, and current and know how to
use the meter correctly.
The
Digital Volt-Ohm Meter is covered in the
"Special Tools" portion of this section.
DIAGNOSTIC INFORMATION
The diagnostic "Trouble Tree" charts and func­
tional checks in this manual are designed to locate
a faulty circuit or component through logic based
on the process
of elimination. The charts are
prepared
with the requirement that the vehicle
functioned correctly at the time of assembly and
that there are no multiple failures.
The Engine Control Module (ECM) performs a
continual self-diagnosis on certain control
functions. This diagnostic capability is
complemented by the diagnostic procedures
contained in this
manual. The ECM's language for
communicating the source of a malfunction is a
system
of Diagnostic Trouble Codes (DTCs). The
DTC(s) are
two or three digit numbers that can
range from12 to
51. When a malfunction is
detected by the ECM, a DTC is set and the
Malfunction Indicator Lamp is illuminated.
"CHECK ENGINE" MALFUNCTION
INDICATOR
LAMP (MIL)
This light is on the instrument panel and has two
functions:
• It is used to tell the driver that a problem has
occurred, and that the
vehicle should be
taken
for service as soon as reasonably
possible.
• It
is used by the technician to read out
'Trouble Codes" to help diagnose system
problems.
As a bulb and system check, the light will come
"ON" with the key "ON" and the engine not
running. When the engine is started, the light will
turn off. If the light remains on, the self-diagnostic
system has detected a
problem. If the problem
goes away, the light will go out in most cases after
10 seconds, but a Trouble Code will remain stored
in the
ECM.
When the light remains "ON" while the engine is
running,
or when a malfunction is suspected due
to a
driveability or emissions problem, a on-board
diagnostic system check
must be performed. The
procedures
for these checks are given in Section
"A". These checks will expose malfunctions
which may
not be detected if other diagnostics
are performed
prematurely.
INTERMITTENT "CHECK ENGINE"
MALFUNCTION INDICATOR
LAMP (MIL)
In the case of an "intermittent" problem, the
"Check Engine"
malfunction indicator lamp will
light
for ten (1 0) seconds and then will go out.
However, the corresponding
trouble code will be
stored in the
memory of the ECM until the battery
positive
voltage to the ECM has been removed.
When unexpected DTC(s) appear during the
DTC
code reading process, one can assume that these
DTC(s) were set by an intermittent malfunction
and could be helpful in diagnosing the system.
An intermittent
DTC may or may not re-set. If it is
an intermittent failure, a DTC Chart is not used.
Consult the "Diagnostic Aids" on the intermittent
trouble code. Section "B" also covers the topic of
"intermittents". A physical inspection of the
applicable sub-system most often will resolve the
problem.
II