Nissan Terrano r20e. Manual — part 102
SEF720X
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
ZD30DDTi
CONSULT-II (Cont’d)
EC-45
Introduction
The engine has an ECM to control major systems such as fuel
injection control, fuel injection timing control, glow control system,
etc. The ECM accepts input signals from sensors and instantly
drives electronic control fuel injection pump. 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,
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 a circuit tester connected should be per-
formed. Follow the “Work Flow”, EC-48.
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, especially
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.
DIAGNOSTIC WORKSHEET
There are many operating conditions that lead to the malfunction
of engine components. A good grasp of such conditions can make
troubleshooting 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 shown below in order to
organize all the information for troubleshooting.
SEF858S
SEF233G
SEF234G
SEF907L
TROUBLE DIAGNOSIS — INTRODUCTION
ZD30DDTi
EC-46
Worksheet sample
MTBL0397
TROUBLE DIAGNOSIS — INTRODUCTION
ZD30DDTi
Introduction (Cont’d)
EC-47
Work Flow
*1
Refer to MA section (“Checking
and Replacing Fuel Filter and
Draining Water”, “ENGINE MAIN-
TENANCE”).
*2
If time data of “SELF-DIAG
RESULTS” is other than “0”, per-
form “TROUBLE DIAGNOSIS
FOR INTERMITTENT INCIDENT”,
EC-78.
*3
If the incident cannot be verified,
perform “TROUBLE DIAGNOSIS
FOR INTERMITTENT INCIDENT”,
EC-78.
*4
If the on board diagnostic system
cannot be performed, check main
power supply and ground circuit.
Refer to “TROUBLE DIAGNOSIS
FOR POWER SUPPLY”, EC-79.
*5
If malfunctioning part cannot be
detected, perform “TROUBLE
DIAGNOSIS FOR INTERMIT-
TENT INCIDENT”, EC-78.
YEC253A
TROUBLE DIAGNOSIS — INTRODUCTION
ZD30DDTi
EC-48
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