SUBARU FORESTER 2004 Service Repair Manual

EN(H4DOTC 2.5)-97
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
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. <Ref. to EN(H4DOTC
2.5)-27, Subaru Select Monitor.>
 OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.Is the value 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 tem-
perature sensor
 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. 2 (+) — Engine ground (
−):Is the voltage more than 10 V? Repair battery
short circuit in har-
ness between ECM
and engine coolant
temperature sen-
sor connector.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. 2 (+) — 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. 2 (+) — Engine ground (
−):Is the voltage more than 4 V? Go to step 5.Repair the har-
ness and connec-
tor.
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(H4DOTC 2.5)-98
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. 1 — Engine ground:Is the resistance less than 5 Ω? Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(H4DOTC 2.5)-
26, Engine Cool-
ant Temperature
Sensor.>Repair the 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(H4DOTC 2.5)-99
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
M: 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(H4DOTC 2.5)-42,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOTC 2.5)-35, OPERATION,
Inspection Mode.>.

EN(H4DOTC 2.5)-100
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
WIRING DIAGRAM:
EN-02364
B317
34
12
B22
125678
131415169101112
34
17181920
B21
123
4
56
78
9
1011 12
1314 15 16
B83
1
23456
B135
567
82 1
94 3
10
24 22 23 2511 12 13 14 15
26 27
2816 17 18 19
20 21
29 30 31 32 33 34 35
B:
B35D6
B135 B: C:
D4 D3
C18
B1 C35
D1 B4
D2
SBF-5
2
1
3
4
E
E57
3
6 4
1
2 2
3
15
16
E
5
EE
B137 D:ECM B309
B136
B122
1
E2 B21
E3 B22 B317
E56B47 35
2 1
4 3
D5C16C29
19122018
MAIN RELAYBATTERY
ELECTRONIC
THROTTLE
CONTROL ELECTRONIC
THROTTLE
CONTROL
RELAY
B83
B122
123456783412
56
B47
B137
567
82 1
94 3
10
22 23 11 12 13 14 15
24 25
2616 17
18 19 20 21
27 28 29 30 31
D:
B136
56
782 1
94 3
10
24 22 23 2511 12 13
1415
26 27
2816
17 18 19 20 21
33 34 29
32 30
31 35
C:
B309
34
12
E57

EN(H4DOTC 2.5)-101
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK SENSOR OUTPUT.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM con-
nector and terminal.
Connector & terminal
(B136) No. 29 (+) — (B136) No. 35 (
−):
3) Check the voltage change by shaking the
harness and connector of ECM, engine har-
ness connector and electronic throttle control
connector.Is the voltage more than 0.4 V? Go to step 2.Go to step 3.
2 CHECK POOR CONTACT.
Check the poor contact in connector between
ECM and electronic throttle control.Is there poor contact in con-
nector between ECM and elec-
tronic throttle control?Repair the poor
contact.Temporary poor
contact occurred,
but it is normal at
present.
3 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Disconnect the connectors from the elec-
tronic throttle control.
4) Measure the resistance between ECM con-
nector and electronic throttle control connector.
Connector & terminal
(B136) No. 16 — (E57) No. 5:Is the resistance less than 1
Ω?Go to step 4.Repair the open
circuit of harness
connector.
4 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 18 — Chassis ground:
(B136) No. 16 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 5.Repair the chassis
short circuit of har-
ness.
5 CHECK POWER SUPPLY OF ELECTRONIC
THROTTLE CONTROL.
1) Connect the ECM connector.
2) Turn the ignition switch to ON.
3) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 5 (+) — Engine ground (
−):
4) Check the voltage change by shaking the
harness and connector of ECM and engine
harness connector while monitoring the value
with voltage meter.Is the voltage 4.5 — 5.5 V? Go to step 6.Repair the poor
contact in ECM con-
nector. Replace the
ECM if defective.
<Ref. to
FU(H4DOTC 2.5)-
41, Engine Con-
trol Module
(ECM).>
6 CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Turn the ignition switch to OFF.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 6 — Engine ground:Is the resistance more than 10
Ω?Repair poor con-
tact of electronic
throttle control
connector.
Replace the elec-
tronic throttle con-
trol if defective.Repair the poor
contact in ECM con-
nector. Replace the
ECM if defective.
<Ref. to
FU(H4DOTC 2.5)-
41, Engine Con-
trol Module
(ECM).>

EN(H4DOTC 2.5)-102
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
N: DTC P0123 THROTTLE/PEDAL POSITION SENSOR/SWITCH “A” CIRCUIT
HIGH 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(H4DOTC 2.5)-42,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOTC 2.5)-35, OPERATION,
Inspection Mode.>.

EN(H4DOTC 2.5)-103
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
WIRING DIAGRAM:
Step Check Yes No
1 CHECK SENSOR OUTPUT.
1) Turn the ignition switch to ON.
2) Read the data of main throttle sensor signal
using Subaru Select Monitor.
3) Check the voltage change by shaking the har-
ness and connector of ECM, engine harness con-
nector and electronic throttle control connector.Is the voltage less than 4.63
V?Go to step 2.Go to step 3.
EN-02364
B317
34
12
B22
125678
131415169101112
34
17181920
B21
123
4
56
78
9
1011 12
1314 15 16
B83
1
23456
B135
567
82 1
94 3
10
24 22 23 2511 12 13 14 15
26 27
2816 17 18 19
20 21
29 30 31 32 33 34 35
B:
B35D6
B135 B: C:
D4 D3
C18
B1 C35
D1 B4
D2
SBF-5
2
1
3
4
E
E57
3
6 4
1
2 2
3
15
16
E
5
EE
B137 D:ECM B309
B136
B122
1
E2 B21
E3 B22 B317
E56B47 35
2 1
4 3
D5C16C29
19122018
MAIN RELAYBATTERY
ELECTRONIC
THROTTLE
CONTROL ELECTRONIC
THROTTLE
CONTROL
RELAY
B83
B122
123456783412
56
B47
B137
567
82 1
94 3
10
22 23 11 12 13 14 15
24 25
2616 17
18 19 20 21
27 28 29 30 31
D:
B136
56
782 1
94 3
10
24 22 23 2511 12 13
1415
26 27
2816
17 18 19 20 21
33 34 29
32 30
31 35
C:
B309
34
12
E57

EN(H4DOTC 2.5)-104
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
2 CHECK POOR CONTACT.
Check the poor contact in connector between
ECM and electronic throttle control.Is there poor contact in con-
nector between ECM and elec-
tronic throttle control?Repair the poor
contact.Temporary poor
contact occurred,
but it is normal at
present.
3 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Disconnect the connectors from the elec-
tronic throttle control.
4) Measure the resistance between ECM con-
nector and electronic throttle control connector.
Connector & terminal
(B136) No. 18 — (E57) No. 6:
(B136) No. 35 — (E57) No. 3:Is the resistance less than 1
Ω?Go to step 4.Repair the open
circuit of harness
connector.
4 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL.
1) Connect the ECM connector.
2) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 3 — Engine ground:Is the resistance less than 1
Ω?Go to step 5.Repair the poor
contact in ECM
connector. Replace
the ECM if defec-
tive. <Ref. to
FU(H4DOTC 2.5)-
41, Engine Con-
trol Module
(ECM).>
5 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL.
1) Turn the ignition switch to ON.
2) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 5 (+) — Engine ground (
−):
3) Check the voltage change by shaking the
harness and connector of ECM and engine
harness connector while monitoring the value
with voltage meter.Is the voltage more than 10 V? Go to step 6.Repair battery
short circuit in har-
ness between
ECM connector
and electronic
throttle control
connector.
6 CHECK SENSOR OUTPUT POWER SUP-
PLY.
1) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 6 (+) — Engine ground (
−):
2) Check the voltage change by shaking the
harness and connector of ECM and engine
harness connector while monitoring the value
with voltage meter.Is the voltage less than 10 V? Go to step 7.Repair battery
short circuit in har-
ness between
ECM connector
and electronic
throttle control
connector.
7 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B136) No. 18 — (B136) No. 16:Is the resistance more than 1
MΩ?Repair poor contact
in harness. Repair
the electronic throt-
tle control.Repair short circuit
to sensor power
supply. Step Check Yes No

EN(H4DOTC 2.5)-105
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
O: DTC P0131 O2 SENSOR CIRCUIT LOW VOLTAGE (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4DOTC 2.5)-42,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOTC 2.5)-35, OPERATION,
Inspection Mode.>.
WIRING DIAGRAM:
EN-02359
SBF-5
B47 1 2 3 5 4 6
E
E
B21
E236
72
3
26
33
25
ECM
B134
1
3 2
4
B262
34 12
56
123
4
56
78
9
1011 12
1314 15 16
B21 B47 B262
B134
56 7
82 1
94 310
24 22 23 25 11 12 13 14 15
26 27
2816 17
18 19 20 21
33 34 29
32 30 31
MAIN RELAY1234BATTERY
FRONT OXYGEN
(A/F) SENSOR

EN(H4DOTC 2.5)-106
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
front oxygen (A/F) sensor connector.
3) Measure the resistance of harness between
ECM and front oxygen (A/F) sensor connector.
Connector & terminal
(B134) No. 26 — Chassis ground:
(B134) No. 33 — Chassis ground:Is the resistance more than 1
MΩ?Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(H4DOTC 2.5)-
36, Front Oxygen
(A/F) Sensor.>Repair ground
short circuit in har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.