Subaru Legacy 2002 Service Manual page 906

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
No.
1 CHECK SPEEDOMETER OPERATION IN
COMBINATION METER.
2 CHECK INPUT SIGNAL FOR ECM.
1) Lift-up the vehicle.
2) Set the positive (+) terminal and earth lead
of oscilloscope at ECM connector terminals.
Connector & terminal
(B135) No. 24 (+) — Chassis ground
(–):
3) Start the engine.
4) Shift on the gear position, and put the
vehicle at constant speed.
5) Measure signal voltage indicated on oscil-
loscope.
3 CHECK POOR CONTACT.
Check poor contact in ECM connector.
4 CHECK HARNESS BETWEEN ECM AND
COMBINATION METER CONNECTOR.
Measure voltage between ECM and chassis
ground.
Connector & terminal
(B135) No. 24 (+) — Chassis ground
(−):
5 CHECK HARNESS BETWEEN ECM AND
COMBINATION METER CONNECTOR.
1) Turn ignition switch to OFF.
2) Measure resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B135) No. 24 — Chassis ground:
6 CHECK POOR CONTACT.
Check poor contact in ECM connector.
Step
Does speedometer operate
normally?
Is the voltage more than 3
V?
Is there poor contact in
ECM connector?
Is the voltage more than 2
V?
Is the resistance less than
10 Ω?
Is there poor contact in
ECM connector?
EN(w/oOBD)-95
Check Yes
Go to step 2.
Go to step 3.
Repair poor con-
tact in ECM.
Repair harness
and connector.
NOTE:
In this case,
repair the follow-
ing:
Battery short cir-
cuit in harness
between ECM
and combination
meter connector
Repair ground
short circuit in
harness between
ECM and combi-
nation meter con-
nector.
Repair poor con-
tact in ECM.
Engine (Diagnostics)
No
Check speedom-
eter and vehicle
speed sensor.
Go to step 4.
Replace ECM.
<Ref. to FU(w/
oOBD)-45, Engine
Control Module.>
Go to step 5.
Go to step 6.
Replace ECM.
<Ref. to FU(w/
oOBD)-45, Engine
Control Module.>