EN(H4SO 2.5)(diag)-81
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
Check
Yes
No
1
CHECK OPTION CODE.
Is the option code EC, EK, EH,
ER or K4?
Go to step 2.
Refer to EN(H4SO
2.0) section. <Ref.
to EN(H4SO
2.0)(diag)-64, 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.
2
CHECK ANY OTHER DTC ON DISPLAY.
Do DTC P0031 and P0037 dis-
play at the same time on the
Subaru Select Monitor?
Go to step 3.
Go to step 6.
3
CHECK POWER SUPPLY TO FRONT OXY-
GEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from front oxygen
(A/F) sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between front oxygen
(A/F) sensor connector and engine ground.
Connector & terminal
(E24) No. 4 (+) — Engine ground (
−
):
Is the voltage more than 10 V? Go to step 4.
Repair the power
supply line.
NOTE:
In this case, repair
the following:
• Open circuit of
harness between
main relay and
front oxygen (A/F)
sensor connector
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
main relay connec-
tor
4
CHECK GROUND CIRCUIT FOR ECM.
Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B134) No. 6 — Chassis ground:
(B134) No. 7 — Chassis ground:
Is the resistance less than 5
Ω?
Go to step 5.
Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit of
harness between
ECM and engine
ground terminal
• Poor contact in
ECM connector
• Poor contact in
coupling connector
5
CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of front oxygen (A/F) sensor
heater current using Subaru Select Monitor or
general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO 2.5)(diag)-25, Subaru Select
Monitor.>
• General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
Is the current more than 0.2 A? Repair the poor
contact in connec-
tor.
NOTE:
In this case, repair
the following:
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
ECM connector
Go to step 6.