Subaru Legacy 2002 Service Manual page 3371

1. Basic Diagnostics Procedure
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A: BASIC PROCEDURES
1. GENERAL
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The most important purpose of diagnostics is to
determine which part is malfunctioning quickly, to
save time and labor.
2. IDENTIFICATION OF TROUBLE
SYMPTOM
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Determine what the problem is based on the symp-
tom.
3. PROBABLE CAUSE OF TROUBLE
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Look at the wiring diagram and check the system's
circuit. Then check the switch, relay, fuse, ground,
etc.
4. LOCATION AND REPAIR OF TROUBLE
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1) Using the diagnostics narrow down the causes.
2) If necessary, use a voltmeter, ohmmeter, etc.
3) Before replacing certain component parts
(switch, relay, etc.), check the power supply,
ground, for open wiring harness, poor connectors,
etc. If no problems are encountered, check the
component parts.
5. CONFIRMATION OF SYSTEM
OPERATION
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After repairing, ensure that the system operates
properly.
B: BASIC INSPECTION
1. VOLTAGE MEASUREMENT
1) Using a voltmeter, connect the negative lead to
a good ground point or negative battery terminal
and the positive lead to the connector or compo-
nent terminal.
2) Contact the positive probe of the voltmeter on
connector (A).
The voltmeter will indicate a voltage.
BASIC DIAGNOSTICS PROCEDURE
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WI-3
3) Shift the positive probe to connector (B). The
voltmeter will indicate no voltage.
4) With test set-up held as it is, turn switch ON.
The voltmeter will indicate a voltage and, at the
same time, the light will come on.
5) The circuit is in good order. If a problem such
as a lamp failing to light occurs, use the proce-
dures outlined above to track down the malfunc-
tion.
2. CIRCUIT CONTINUITY CHECKS
1) Disconnect the battery terminal or connector so
there is no voltage between the check points.
Contact the two leads of an ohmmeter to each of
the check points.
If the circuit has diodes, reverse the two leads and
check again.
2) Use an ohmmeter to check for diode continuity.
When contacting the negative lead to the diode
positive side and the positive lead to the negative
side, there should be continuity.
When contacting the two leads in reverse, there
should be no continuity.
Wiring System
H6M0510A
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G6M0207