2004 SUBARU FORESTER check engine light

EN(H4SO)-113
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of throttle position sensor
signal using Subaru Select Monitor or OBD-II
general scan tool.
N
OTE:
 Subaru Select Monitor
For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. to EN(H4SO)-29, Subaru Select Monitor.>
 OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.Is the voltage less than 0.1 V? Go to step 2.Even if the mal-
function indicator
light illuminates,
the circuit has
returned to a nor-
mal condition at
this time. A tempo-
rary poor contact
of the connector
may be the cause.
N
OTE:
In this case repair
the following:
 Poor contact in
throttle position
sensor connector
 Poor contact in
ECM connector.
 Poor contact in
coupling connector
2 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground while throttle valve is fully
closed.
Connector & terminal
(B135) No. 3 (+) — Chassis ground (
−):Is the voltage more than 4.5 V? Go to step 4.Go to step 3.
3 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B135) No. 3 (+) — Chassis ground (
−):Is the voltage more than 4.5 V
by shaking the ECM harness
and connector?Repair the poor
contact in ECM
connector.Contact the SUB-
ARU dealer.
N
OTE:
Inspection by DTM
is required, because
probable cause is
deterioration of mul-
tiple parts.
4 CHECK INPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B135) No. 13 (+) — Chassis ground (
−):Is the voltage less than 0.1 V? Go to step 6.Go to step 5.
5 CHECK INPUT SIGNAL FOR ECM (WITH
SUBARU SELECT MONITOR).
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B135) No. 13 (+) — Chassis ground (
−):Is the voltage more than 0.1 V
by shaking the ECM harness
and connector?Repair the poor
contact in ECM
connector.Go to step 6.

EN(H4SO)-116
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of throttle position sensor
signal using Subaru Select Monitor or OBD-II
general scan tool.
N
OTE:
 Subaru Select Monitor
For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. to EN(H4SO)-29, Subaru Select Monitor.>
 OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.Is the voltage more than 4.9 V? Go to step 2.Even if the mal-
function indicator
light illuminates,
the circuit has
returned to a nor-
mal condition at
this time. A tempo-
rary poor contact
of the connector
may be the cause.
N
OTE:
In this case repair
the following:
 Poor contact in
throttle position
sensor connector
 Poor contact in
ECM connector.
 Poor contact in
coupling connector
2 CHECK HARNESS BETWEEN THROTTLE
POSITION SENSOR AND ECM CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from throttle
position sensor.
3) Measure the resistance of harness
between throttle position sensor connector and
engine ground.
Connector & terminal
(E13) No. 2 — Engine ground:Is the resistance less than 5
Ω?Go to step 3.Repair harness
and connector.
NOTE:
In this case repair
the following:
 Open circuit in
harness between
throttle position
sensor and ECM
connector
 Poor contact in
coupling connector
 Poor contact in
joint connector
3 CHECK HARNESS BETWEEN THROTTLE
POSITION SENSOR AND ECM CONNEC-
TOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between throttle posi-
tion sensor connector and engine ground.
Connector & terminal
(E13) No. 3 (+) — Engine ground (
−):Is the voltage more than 4.9 V? Repair the battery
short circuit in har-
ness between
throttle position
sensor and ECM
connector. After
repair, replace the
ECM. FU(H4SO)-44,
Engine Control
Module (ECM).>Replace the throt-
tle position sen-
sor. FU(H4SO)-29,
Throttle Position
Sensor.>

EN(H4SO)-145
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
13 CHECK STATUS OF MALFUNCTION INDI-
CATOR LIGHT.
1) Clear the memory using Subaru Select
Monitor.

2) Start the engine, and drive the vehicle more
than 10 minutes.Does the malfunction indicator
light illuminate or blink?Go to step 15.Go to step 14.
14 CHECK CAUSE OF MISFIRE DIAGNOSED.Was the cause of misfire diag-
nosed when the engine is run-
ning? Ex. Removed spark plug
cord, etc.Finish diagnostics
operation, if the
engine has no
abnormality.1. Repair the poor
contact.
N
OTE:
In this case repair
the following:
 Poor contact in
ignitor connector
 Poor contact in
ignition coil con-
nector
 Poor contact in
fuel injector con-
nector on faulty
cylinders
 Poor contact in
ECM connector.
 Poor contact in
coupling connector
2. If there is no
poor contact,
check the following
items and contact
SUBARU dealer.
 Fuel condi-
tion
 Contained
additive
 Plug condi-
tion
Plug cord
condition
 Engine oil
condition
15 CHECK AIR INTAKE SYSTEM.Is there any fault in air intake
system?Repair air intake
system.
N
OTE:
Check the follow-
ing items:
 Are there air
leaks or air suction
caused by loose or
dislocated nuts
and bolts?
 Are there cracks
or any disconnec-
tion of hoses?Go to step 16. Step Check Yes No

EN(H4SO)-151
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK HARNESS BETWEEN KNOCK SEN-
SOR AND ECM CONNECTOR.
Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B135) No. 16 — Chassis ground:Is the resistance less than 400
kΩ?Go to step 2.Go to step 3.
2 CHECK KNOCK SENSOR.
1) Disconnect the connector from knock sen-
sor.
2) Measure the resistance between knock
sensor connector terminal and engine ground.
Te r m i n a l s
No. 2 — Engine ground:Is the resistance less than 400
kΩ?Replace the knock
sensor. FU(H4SO)-28,
Knock Sensor.>Repair ground
short circuit in har-
ness between
knock sensor con-
nector and ECM
connector.
N
OTE:
The harness be-
tween both connec-
tors are shielded.
Repair short circuit
in harness covered
with shield.
3 CHECK INPUT SIGNAL FROM ECM.
1) Connect the connectors to ECM and knock
sensor.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B135) No. 16 (+) — Chassis ground (
−):Is the voltage more than 2 V? Even if the mal-
function indicator
light illuminates,
the circuit has
returned to a nor-
mal condition at
this time. (How-
ever, the possibility
of poor contact still
remains.)
N
OTE:
In this case repair
the following:
 Poor contact in
knock sensor con-
nector
 Poor contact in
ECM connector.
 Poor contact in
coupling connectorRepair the poor
contact in ECM
connector.

EN(H4SO)-163
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
6 CHECK HARNESS BETWEEN EGR VALVE
AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Detach the connector from EGR valve and
ECM.
3) Measure the resistance of harness
between EGR valve and ECM connector.
Connector & terminal
(B134) No. 18 — (E18) No. 6:
(B134) No. 17 — (E18) No. 1:
(B134) No. 16 — (E18) No. 4:
(B134) No. 15 — (E18) No. 3:Is the resistance less than 1
Ω?Go to step 7.Repair open circuit
in harness
between ECM and
EGR valve con-
nector.
7 CHECK HARNESS BETWEEN EGR VALVE
AND ECM CONNECTOR.
Measure the resistance of harness between
EGR valve and chassis ground.
Connector & terminal
(B134) No. 15 — Chassis ground:
(B134) No. 16 — Chassis ground:
(B134) No. 17 — Chassis ground:
(B134) No. 18 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 8.Repair short circuit
in harness
between main
relay and EGR
valve connector.
8 CHECK POOR CONTACT.
Check that the poor contact of ECM and EGR
valve connector.Is there poor contact of ECM
and EGR valve connector?Repair the poor
contact portion of
ECM and EGR
valve connector.Even if the mal-
function indicator
light illuminates,
the circuit has
returned to a spec-
ified condition at
this time. Step Check Yes No

EN(H4SO)-167
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK OUTPUT SIGNAL FROM ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B134) No. 29 (+) — Chassis ground (
−):Is the voltage more than 10 V? Even if the mal-
function indicator
light illuminates,
the circuit has
returned to a nor-
mal condition at
this time. Contact
the SUBARU
dealer.
N
OTE:
Inspection by DTM
is required, because
probable cause is
deterioration of mul-
tiple parts.Go to step 2.
2 CHECK HARNESS BETWEEN PURGE CON-
TROL SOLENOID VALVE AND ECM CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from purge con-
trol solenoid valve and ECM.
3) Measure the resistance of harness
between purge control solenoid valve connec-
tor and engine ground.
Connector & terminal
(E4) No. 2 — Engine ground:Is the resistance more than 1
MΩ?Go to step 3.Repair ground
short circuit in har-
ness between
ECM and purge
control solenoid
valve connector.
3 CHECK HARNESS BETWEEN PURGE CON-
TROL SOLENOID VALVE AND ECM CON-
NECTOR.
Measure the resistance of harness between
ECM and purge control solenoid valve of har-
ness connector.
Connector & terminal
(B134) No. 29 — (E4) No. 2:Is the resistance less than 1
Ω?Go to step 4.Repair open circuit
in harness
between ECM and
purge control sole-
noid valve connec-
tor.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
ECM and purge
control solenoid
valve connector
 Poor contact in
coupling connector
4 CHECK PURGE CONTROL SOLENOID
VALVE.
1) Remove the purge control solenoid valve.
2) Measure the resistance between purge
control solenoid valve terminals.
Te r m i n a l s
No. 1 — No. 2:Is the resistance 10 — 100 Ω? Go to step 5.Replace the purge
control solenoid
valve. EC(H4SO)-9,
Purge Control
Solenoid Valve.>
5 CHECK POWER SUPPLY TO PURGE CON-
TROL SOLENOID VALVE.
1) Turn the ignition switch to ON.
2) Measure the voltage between purge control
solenoid valve and engine ground.
Connector & terminal
(E4) No. 1 (+) — Engine ground (
−):Is the voltage more than 10 V? Go to step 6.Repair open circuit
in harness
between main
relay and purge
control solenoid
valve connector.

EN(H4SO)-170
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK OUTPUT SIGNAL FROM ECM.
1) Turn the ignition switch to OFF.
2) Connect the test mode connector at the
lower portion of instrument panel (on the
driver’s side).
3) Turn the ignition switch to ON.
4) While operating the purge control solenoid
valve, measure voltage between ECM and
chassis ground.
N
OTE:
Purge control solenoid valve operation can be
executed using Subaru Select Monitor. Refer to
“Compulsory Valve Operation Check Mode” for
procedures. sory Valve Operation Check Mode.>
Connector & terminal
(B134) No. 29 (+) — Chassis ground (
−):Is the voltage 0 — 10 V? Go to step 2.Even if the mal-
function indicator
light illuminates,
the circuit has
returned to a nor-
mal condition at
this time. In this
case, repair poor
contact in ECM
connector.
2 CHECK OUTPUT SIGNAL FROM ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B137) No. 29 (+) — Chassis ground (
−):Is the voltage more than 10 V? Go to step 4.Go to step 3.
3 CHECK POOR CONTACT.
Check poor contact in ECM connector. Is there poor contact in ECM
connector?Repair the poor
contact in ECM
connector.Replace the ECM.
FU(H4SO)-44,
Engine Control
Module (ECM).>
4 CHECK HARNESS BETWEEN PURGE CON-
TROL SOLENOID VALVE AND ECM CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from purge con-
trol solenoid valve.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B134) No. 29 (+) — Chassis ground (
−):Is the voltage more than 10 V? Repair battery
short circuit in har-
ness between
ECM and purge
control solenoid
valve connector.
After repair,
replace the ECM.
FU(H4SO)-44,
Engine Control
Module (ECM).>Go to step 5.
5 CHECK PURGE CONTROL SOLENOID
VALVE.
1) Turn the ignition switch to OFF.
2) Measure the resistance between purge
control solenoid valve terminals.
Te r m i n a l s
No. 1 — No. 2:Is the resistance less than 1
Ω?Replace the purge
control solenoid
valve EC(H4SO)-9,
Purge Control
Solenoid Valve.>
and ECM. FU(H4SO)-44,
Engine Control
Module (ECM).>Go to step 6.
6 CHECK POOR CONTACT.
Check poor contact in ECM connector.Is there poor contact in ECM
connector?Repair the poor
contact in ECM
connector.Replace the ECM.
FU(H4SO)-44,
Engine Control
Module (ECM).>

ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK SPEEDOMETER AND TACHOME- TER OPERATION IN COMBINATION
METER. Does the speedometer and
tachometer operate normally?
Go to step
2.Repair or replace
the combination
meter. 3, Combination
Meter System.>
2 CHECK INPUT SIGNAL FROM ECM. 1) Turn the ignition switch to ON. (engine
OFF)
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal (B135) No. 25 (+) — Chassis ground (
−): Is the voltage less than 0.12
V?
Go to step
4.Go to step 3.
3 CHECK INPUT SIGNAL FOR ECM (WITH SUBARU SELECT MONITOR).
Read the data of fuel level sensor signal using
Subaru Select Monitor.
N
OTE:
For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. to EN(H4SO)-29, Subaru Select Monitor.> Is the voltage less than 0.12 V
by shaking the ECM harness
and connector?
Repair the poor
contact in ECM
connector.Even if the mal-
function indicator
light illuminates,
the circuit has
returned to a nor-
mal condition at
this time. A tempo-
rary poor contact
of the connector
may be the cause.
NOTE:
In this case repair
the following:
 Poor contact in
combination meter
connector
 Poor contact in
ECM connector.
 Poor contact in
coupling connector
4 CHECK INPUT VOLTAGE OF ECM. 1) Turn the ignition switch to OFF.
2) Separate fuel tank cord connector (R57)
and rear wiring harness connector (R15).
3) Turn the ignition switch to ON.
4) Measure the voltage of harness between
ECM connector and chassis ground.Connector & terminal
(B135) No. 25 (+) — Chassis ground (
−): Is the voltage more than 0.12
V?
Go to step
5.Go to step 6.
5 CHECK HARNESS BETWEEN ECM AND COMBINATION METER.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from connector
(i10) and ECM connector.
3) Measure the resistance between ECM and
chassis ground.Connector & terminal (B135) No. 25 — Chassis ground: Is the resistance more than 1
M
Ω? Go to step
7.Repair the ground
short in harness
between ECM and
combination meter
connector.
6 CHECK HARNESS BETWEEN ECM AND COMBINATION METER.
Measure the resistance between ECM and
combination meter connector.Connector & terminal (B135) No. 25 — (i11) No. 1: Is the resistance less than 10
Ω
? Repair or replace
the combination
meter. 3, Combination
Meter System.>Repair open circuit
between ECM and
combination meter
connector.
NOTE:
In this case repair
the following:
Poor contact in
coupling connector
EN(H4SO)-174