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MEF036D
SEF233G
SEF234G
Introduction
NGEC0557
The engine has an ECM to control major systems such as fuel
control, ignition control, idle air control system, etc. The ECM
accepts input signals from sensors and instantly drives actuators.
It is essential that both input and output signals are proper and
stable. At the same time, it is important that there are no problems
such as vacuum leaks, fouled spark plugs, or other problems with
the engine.
It is much more difficult to diagnose a problem that occurs intermit-
tently rather than continuously. Most intermittent problems are
caused by poor electric connections or improper wiring. In this
case, careful checking of suspected circuits may help prevent the
replacement of good parts.
A visual check only may not find the cause of the problems. A road
test with CONSULT-II (or GST) or a circuit tester connected should
be performed. Follow the “Work Flow” on EC-692.
Before undertaking actual checks, take a few minutes to talk with
a customer who approaches with a driveability complaint. The cus-
tomer can supply good information about such problems, espe-
cially intermittent ones. Find out what symptoms are present and
under what conditions they occur.A“Diagnostic Worksheet” like the
example on next page should be used.
Start your diagnosis by looking for “conventional” problems first.
This will help troubleshoot driveability problems on an electronically
controlled engine vehicle.
SEF907L
DIAGNOSTIC WORKSHEET
NGEC0557S01
There are many operating conditions that lead to the malfunction
of engine components. A good grasp of such conditions can make
trouble-shooting faster and more accurate.
In general, each customer feels differently about a problem. It is
important to fully understand the symptoms or conditions for a
customer complaint.
Utilize a diagnostic worksheet like the one on the next page in order
to organize all the information for troubleshooting.
Some conditions may cause the MILto come on steady or blink and
DTC to be detected. Examples:
쐌 Vehicle ran out of fuel, which caused the engine to misfire.
쐌 Fuel filler cap was left off or incorrectly screwed on, allowing
fuel to evaporate into the atmosphere [for the models with
EVAP (SMALL LEAK) diagnosis].
TROUBLE DIAGNOSIS — INTRODUCTION
VG33E
EC-690
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