Subaru Impreza 2002 Service Manual page 3742

1. Basic Diagnostics Procedure
A: BASIC PROCEDURES
1. GENERAL
The most important purpose of diagnostics is to de-
termine which part is malfunctioning quickly, to
save time and labor.
2. IDENTIFICATION OF TROUBLE SYMP-
TOM
Determine what the problem is based on symptom.
3. PROBABLE CAUSE OF TROUBLE
Look at the wiring diagram and check system's cir-
cuit. Then check the switch, relay, fuse, ground,
etc.
4. LOCATION AND REPAIR OF TROUBLE
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 OPERA-
TION
After repairing, ensure that the system operates
properly.
BASIC DIAGNOSTICS PROCEDURE
WI-3
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 component ter-
minal.
2) Contact the positive probe of the voltmeter on
connector (A).
The voltmeter will indicate a voltage.
3) Shift the positive probe to connector (B). The
voltmeter will indicate no voltage.
4) With test set-up held as it is, turn the 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 procedures
outlined above to track down malfunction.
WIRING SYSTEM
H6M0510A