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HOW TO DIAGNOSE
HOW
TO
DIAGNOSE
The most important point in troubleshooting is to determine “Probable Causes”. Once the probable causes
are determined, parts to be checked can be limited to those associated with such probable causes. Therefore,
unnecessary checks can be eliminated. The determination of the probable causes must be based on a theory
and be supported by facts and must not be based on intuition only.
ii
TROUBLESHOOTING STEPS
If an attempt is made to solve a problem without going through correct steps for troubleshooting, the problem
symptoms could become more complicated, resulting in failure to determine the causes correctly and making
incorrect repairs. The four steps below should be followed in troubleshooting.
11
1
~~;~;t~;~~toms
1
Observe the symptom carefully.
Check
If
there are also other problems.
In determining the probable causes, it is necessary to
check the wiring diagram to understand the circuit as a
system. Knowledge of switches, relays and other parts is
necessary for accurate determination. The causes of
similar problems in the past must be taken into account.
3
L
Checking of Parts Associated
with Probable Causes and
Determination of Faulty Parts
I
Troubleshooting is carried out by making step by step
checks until the true cause is found. Always go through
the procedures considering what check is to be made
where for the best results.
‘4
1
1
Repair and Confirmation
1
After the problems are corrected, be sure to check that
the system operates correctly. Also, check that new
problems have not been caused by the repair.
INFORMATION FOR DIAGNOSIS
This manual contains the cable diagrams as well as the individual circuit drawings, operational explanations,
and troubleshooting hints for each component required to facilitate the task of troubleshooting. The
information is compiled in the following manner:
(1)
Cable diagrams show the connector positions, etc., on the actual vehicle as well as the harness path.
(2) Circuit drawings show the configuration of the circuit with all switches in their normal positions.
(3) Operational explanations include circuit drawings of voltage flow when the switch is operated and how
the component operates in reaction.
(4) Troubleshooting hints include numerous examples of problems which might occur, traced backward in a
common-sense manner to the origin of the trouble.
Problems whose origins may not be found in this manner are pursued through the various system circuits.
NOTE
Components of MFI, ETACS, ECS, etc. with ECU do not include 3 and 4 above. For this information, refer
to a manual which includes details of these components.
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