SUBARU FORESTER 2004 Service Repair Manual

EN(H4SO)-103
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 intake air temperature
sensor signal using Subaru Select Monitor or
the OBD-II general scan tool.
N
OTE:
 Subaru Select Monitor
For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO)-29, Subaru Select Monitor.>
 OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II Scan Tool Instruction Manual.Is the intake air temperature
less than −40°C (−40°F)?Go to step 2.Repair the poor
contact.
N
OTE:
In this case repair
the following:
 Poor contact in
mass air flow and
intake air tempera-
ture sensor
 Poor contact in
ECM
 Poor contact in
coupling connector
 Poor contact in
joint connector
2 CHECK HARNESS BETWEEN INTAKE AIR
TEMPERATURE SENSOR AND ECM CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector intake air temper-
ature sensor.
3) Measure the voltage between intake air
temperature sensor connector and engine
ground.
Connector & terminal
(E20) No. 1 (+) — Engine ground (
−):Is the voltage more than 10 V? Repair battery
short circuit in har-
ness between
intake air tempera-
ture sensor and
ECM connector.Go to step 3.
3 CHECK HARNESS BETWEEN INTAKE AIR
TEMPERATURE SENSOR AND ECM CON-
NECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between intake air
temperature sensor connector and engine
ground.
Connector & terminal
(E20) No. 1 (+) — Engine ground (
−):Is the voltage more than 10 V? Repair battery
short circuit in har-
ness between
intake air tempera-
ture sensor and
ECM connector.Go to step 4.
4 CHECK HARNESS BETWEEN INTAKE AIR
TEMPERATURE SENSOR AND ECM CON-
NECTOR.
Measure the voltage between intake air tem-
perature sensor connector and engine ground.
Connector & terminal
(E20) No. 1 (+) — Engine ground (
−):Is the voltage more than 3 V? Go to step 5.Repair harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector
 Poor contact in
mass air flow and
intake air tempera-
ture sensor
 Poor contact in
ECM
 Poor contact in
coupling connector
 Poor contact in
joint connector

EN(H4SO)-104
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
5 CHECK HARNESS BETWEEN INTAKE AIR
TEMPERATURE SENSOR AND ECM CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness
between intake air temperature sensor con-
nector and engine ground.
Connector & terminal
(E20) No. 2 — Engine ground:Is the resistance less than 5
Ω?Replace the intake
air temperature
sensor. <Ref. to
FU(H4SO)-32,
Intake Air Temper-
ature Sensor.>Repair harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector
 Poor contact in
mass air flow and
intake air tempera-
ture sensor
 Poor contact in
ECM
 Poor contact in
joint connector Step Check Yes No

EN(H4SO)-105
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
L: DTC P0117 ENGINE COOLANT TEMPERATURE CIRCUIT LOW INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
 Hard to start
 Erroneous idling
 Poor driving performance
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4SO)-44, OP-
ERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO)-37, OPERATION, Inspec-
tion Mode.>.
WIRING DIAGRAM:
EN-02388
1
2
B122
1912
913
B135ECM
21
E3
B22
E8 ENGINE
COOLANT
TEMPERATURE
SENSOR
E8
12
3
B135
567
82 1
94
310
24 22 23 251112131415
26 27
281617181920 21
B22
125678
131415169101112
34
17181920
B122 : LHD
12345678
B122 : RHD
1234

EN(H4SO)-106
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 engine coolant tempera-
ture sensor signal using Subaru Select Monitor
or the OBD-II general scan tool.
N
OTE:
 Subaru Select Monitor
For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO)-29, Subaru Select Monitor.>
 OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II Scan Tool Instruction Manual.Is engine coolant temperature
more than 150°C (302°F)?Go to step 2.Repair the poor
contact.
N
OTE:
In this case repair
the following:
 Poor contact in
engine coolant
temperature sen-
sor
 Poor contact in
ECM
 Poor contact in
coupling connector
 Poor contact in
joint connector
2 CHECK HARNESS BETWEEN ENGINE
COOLANT TEMPERATURE SENSOR AND
ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the engine
coolant temperature sensor.
3) Turn the ignition switch to ON.
4) Read the data of engine coolant tempera-
ture sensor signal using Subaru Select Monitor
or the OBD-II general scan tool.
NOTE:
 Subaru Select Monitor
For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO)-29, Subaru Select Monitor.>
 OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II Scan Tool Instruction Manual.Is engine coolant temperature
less than −40°C (−40°F)?Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(H4SO)-25,
Engine Coolant
Temperature Sen-
sor.>Repair ground
short circuit in har-
ness between
engine coolant
temperature sen-
sor and ECM con-
nector.

EN(H4SO)-107
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
M: DTC P0118 ENGINE COOLANT TEMPERATURE CIRCUIT HIGH INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
 Hard to start
 Erroneous idling
 Poor driving performance
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4SO)-44, OP-
ERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO)-37, OPERATION, Inspec-
tion Mode.>.
WIRING DIAGRAM:
EN-02388
1
2
B122
1912
913
B135ECM
21
E3
B22
E8 ENGINE
COOLANT
TEMPERATURE
SENSOR
E8
12
3
B135
567
82 1
94
310
24 22 23 251112131415
26 27
281617181920 21
B22
125678
131415169101112
34
17181920
B122 : LHD
12345678
B122 : RHD
1234

EN(H4SO)-108
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 engine coolant tempera-
ture sensor signal using Subaru Select Monitor
or the OBD-II general scan tool.
N
OTE:
 Subaru Select Monitor
For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO)-29, Subaru Select Monitor.>
 OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II Scan Tool Instruction Manual.Is engine coolant temperature
less than −40°C (−40°F)?Go to step 2.Repair the poor
contact.
N
OTE:
In this case repair
the following:
 Poor contact in
engine coolant
temperature sen-
sor
 Poor contact in
ECM
 Poor contact in
coupling connector
 Poor contact in
joint connector
2 CHECK HARNESS BETWEEN ENGINE
COOLANT TEMPERATURE SENSOR AND
ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the engine
coolant temperature sensor.
3) Measure the voltage between engine cool-
ant temperature sensor connector and engine
ground.
Connector & terminal
(E8) No. 1 (+) — Engine ground (
−):Is the voltage more than 10 V? Repair battery
short circuit in har-
ness between
ECM and engine
coolant tempera-
ture sensor con-
nector.Go to step 3.
3 CHECK HARNESS BETWEEN ENGINE
COOLANT TEMPERATURE SENSOR AND
ECM CONNECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between engine cool-
ant temperature sensor connector and engine
ground.
Connector & terminal
(E8) No. 1 (+) — Engine ground (
−):Is the voltage more than 10 V? Repair battery
short circuit in har-
ness between
ECM and engine
coolant tempera-
ture sensor con-
nector.Go to step 4.
4 CHECK HARNESS BETWEEN ENGINE
COOLANT TEMPERATURE SENSOR AND
ECM CONNECTOR.
Measure the voltage between engine coolant
temperature sensor connector and engine
ground.
Connector & terminal
(E8) No. 1 (+) — Engine ground (
−):Is the voltage more than 4 V? Go to step 5.Repair harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
ECM and engine
coolant tempera-
ture sensor con-
nector
 Poor contact in
engine coolant
temperature sen-
sor connector
 Poor contact in
ECM connector.
 Poor contact in
coupling connector
 Poor contact in
joint connector

EN(H4SO)-109
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
5 CHECK HARNESS BETWEEN ENGINE
COOLANT TEMPERATURE SENSOR AND
ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness
between engine coolant temperature sensor
connector and engine ground.
Connector & terminal
(E8) No. 2 — Engine ground:Is the resistance less than 5
Ω?Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(H4SO)-25,
Engine Coolant
Temperature Sen-
sor.>Repair harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
ECM and engine
coolant tempera-
ture sensor con-
nector
 Poor contact in
engine coolant
temperature sen-
sor connector
 Poor contact in
ECM connector.
 Poor contact in
coupling connector
 Poor contact in
joint connector Step Check Yes No

EN(H4SO)-110
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
N: DTC P0121 THROTTLE/PEDAL POSITION SENSOR/SWITCH “A” CIRCUIT
RANGE/PERFORMANCE
DTC DETECTING CONDITION:
Two consecutive driving cycles with fault
TROUBLE SYMPTOM:
 Erroneous idling
 Engine stalls
 Poor driving performance
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4SO)-44, OP-
ERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO)-37, OPERATION, Inspec-
tion Mode.>.
WIRING DIAGRAM:
EN-02389
19133
91112
B135
234
B22
E3
E13 THROTTLE
POSITION
SENSOR
1
2
B135
ECM
B22
125678
131415169101112
34
17181920B122
E13
1234
567
82 1
94
310
24 22 23 251112131415
26 27
281617181920 21
B122 : LHD
12345678
B122 : RHD
1234

EN(H4SO)-111
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK ANY OTHER DTC ON DISPLAY.Is any other DTC displayed? Inspect the DTC
P0122 or P0123
using “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(H4SO)-72, List
of Diagnostic Trou-
ble Code (DTC).>
N
OTE:
In this case, it is
not necessary to
inspect DTC
P0121.Replace the throt-
tle position sen-
sor. <Ref. to
FU(H4SO)-29,
Throttle Position
Sensor.>

EN(H4SO)-112
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
O: DTC P0122 THROTTLE/PEDAL POSITION SENSOR/SWITCH “A” CIRCUIT
LOW INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
 Erroneous idling
 Engine stalls
 Poor driving performance
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4SO)-44, OP-
ERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO)-37, OPERATION, Inspec-
tion Mode.>.
WIRING DIAGRAM:
EN-02389
19133
91112
B135
234
B22
E3
E13 THROTTLE
POSITION
SENSOR
1
2
B135
ECM
B22
125678
131415169101112
34
17181920B122
E13
1234
567
82 1
94
310
24 22 23 251112131415
26 27
281617181920 21
B122 : LHD
12345678
B122 : RHD
1234