Subaru Legacy 2004 Service Manual page 840

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK OPTION CODE.
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Start and warm-up the engine.
2) Turn the ignition switch to OFF.
3) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
4) Measure the resistance of harness
between ECM and front oxygen (A/F) sensor
connector.
Connector & terminal
(B134) No. 2 — (E24) No. 6:
(B134) No. 3 — (E24) No. 6:
3 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance of harness between
ECM and front oxygen (A/F) sensor connector.
Connector & terminal
(B134) No. 26 — (E24) No. 1:
(B134) No. 33 — (E24) No. 3:
4 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance of harness between
main relay and front oxygen (A/F) sensor con-
nector.
Connector & terminal
(B327) No. 4 — (E24) No. 4:
5 CHECK FRONT OXYGEN (A/F) SENSOR.
Measure the resistance between front oxygen
(A/F) sensor connector terminals.
Terminals
No. 4 — No. 6:
6 CHECK POOR CONTACT.
Check the poor contact in ECM and front oxy-
gen (A/F) sensor connector.
Check
Is the option code EC, EK or
K4?
Is the resistance less than 1
!?
Is the resistance less than 1
!?
Is the resistance less than 1
!?
Is the resistance less than 5
!?
Is there poor contact in ECM or
front oxygen (A/F) sensor con-
nector?
EN(H4SO 2.5)(diag)-81
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Refer to EN(H4SO
2.0) section. <Ref.
to EN(H4SO
2.0)(diag)-66, List
of Diagnostic Trou-
ble Code (DTC).>
NOTE:
Fuel injection sys-
tem for KA and KS
model is the same
as 2.0 L model.
Go to step 3. Repair the open
circuit in harness
between ECM and
front oxygen (A/F)
sensor connector.
Go to step 4. Repair the open
circuit in harness
between ECM and
front oxygen (A/F)
sensor connector.
Go to step 5. Repair the open
circuit in harness
between ECM and
front oxygen (A/F)
sensor connector.
Go to step 6. Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(H4SO 2.5)-34,
Front Oxygen (A/
F) Sensor.>
Repair the poor Replace the front
contact in ECM or oxygen (A/F) sen-
front oxygen (A/F) sor. <Ref. to
sensor connector. FU(H4SO 2.5)-34,
Front Oxygen (A/
F) Sensor.>
No