SUBARU FORESTER 2004 Service Repair Manual

EN(H4SO)-83
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
C: DTC P0032 HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Detect as soon as the malfunction occurs.
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode ERATION, Clear Memory Mode.> and Inspection Mode tion Mode.>.
WIRING DIAGRAM:
EN-02384
B18
3412
56
B47F44
12345678
B136B135
1234
B21
123
4
56
78
9
1011 12
1314 15 16
SBF-5
EE
B47
B18
6
4
5
3
2
1
B23 C13
C22C6 C17
C16
C5
8
B:
C:B135
B136
B21
E2 ECMBATTERY
B61F44
7
FRONT OXYGEN
(A/F) SENSOR MAIN RELAY
567
82 1
94
310
24
22 23251112131415
26 27
281617181920 21
5
2
84
3923 20 211011
221617
24
2512136
261915
14
1
7
18
LHDLHD
RHDRHD
4
3
1 2
B: C:

EN(H4SO)-84
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 con-
nector and chassis ground.
Connector & terminal
(B136) No. 6 (+) — Chassis ground (
−):
(B136) No. 17 (+) — Chassis ground (
−):Is the voltage more than 8 V? Go to step 2.Go to step 3.
2 CHECK FRONT OXYGEN (A/F) SENSOR
HEATER CURRENT.
1) Turn the ignition switch to OFF.
2) Repair battery short circuit in harness
between ECM and front oxygen (A/F) sensor
connector.
3) Turn the ignition switch to ON.
4) Read the data of front oxygen (A/F) sensor
heater current 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 current more than 2.3 A? Replace the ECM.
FU(H4SO)-44,
Engine Control
Module (ECM).>END.
3 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 6 (+) — Chassis ground (
−):
(B136) No. 17 (+) — Chassis ground (
−):Is the voltage more than 8 V by
shaking the ECM harness and
connector?Repair battery
short circuit in har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.END.

EN(H4SO)-85
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
D: DTC P0037 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Two consecutive driving cycles with fault
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode ERATION, Clear Memory Mode.> and Inspection Mode tion Mode.>.
WIRING DIAGRAM:
EN-02385
BATTERYB61F44
7
B47 MAIN RELAY
12
35
46
B61
12345678
C4B14B19D15
C16C5
REAR
OXYGEN SENSOR
ECM
1432
8B21
B122
T6
E2
B47
T6B21
12 34
56 78
9
10 11 12
13 14 15 16
3456
12
1
B135 B:
D:
B137
SBF-5
C:B136
B122 : LHDB122 : RHDB137
4
1
53
2618 15 167891011
17 19
20121314
B135
567
82
94
310
24 22 23 251112131415
26 27
281617181920 21
B136
5
2
84
3923 20 211011
221617
24
2512136
261915
14
1
7
18
LHD
LHD
RHD
RHD1 8
4
143
T5
B19
2
B19T5
B122
T5
34
12
LHDLHD
RHDRHD
1234
123456781234
B:
D:C:

EN(H4SO)-86
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK GROUND CIRCUIT FOR ECM.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM connector and chassis ground.
Connector & terminal
(B136) No. 16 — Chassis ground:
(B136) No. 5 — Chassis ground:Is the resistance less than 5
Ω?Go to step 2.Repair harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
ECM and engine
ground terminal
 Poor contact in
ECM connector.
 Poor contact in
coupling connector
2 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of rear oxygen (A/F) sensor
heater current 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 current more than 0.2 A? Repair the con-
nector.
N
OTE:
In this case repair
the following:
 Poor contact in
rear oxygen sen-
sor connector
 Poor contact in
rear oxygen sen-
sor connecting
harness connector
 Poor contact in
ECM connector.Go to step 3.
3 CHECK OUTPUT SIGNAL FROM ECM.
1) Start and idle the engine.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 4 (+) — Chassis ground (
−):Is the voltage less than 1 V? Go to step 6.Go to step 4.
4 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 4 (+) — Chassis ground (
−):Does the voltage change
within the range of 1 V by
shaking the ECM harness and
connector while monitoring the
value of voltage meter?Repair the poor
contact in ECM
connector.Go to step 5.
5 CHECK OUTPUT SIGNAL FROM ECM.
1) Disconnect the connector from rear oxygen
sensor.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 4 (+) — Chassis ground (
−):Is the voltage less than 1 V? Replace the ECM.
FU(H4SO)-44,
Engine Control
Module (ECM).>Repair battery
short circuit in har-
ness between
ECM and rear oxy-
gen sensor con-
nector. After
repair, replace the
ECM. FU(H4SO)-44,
Engine Control
Module (ECM).>

EN(H4SO)-87
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
6 CHECK POWER SUPPLY TO REAR OXY-
GEN SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from rear oxygen
sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(T6) No. 2 (+) — Chassis ground (
−):Is the voltage more than 10 V? Go to step 7.Repair the power
supply line.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
main relay and
rear oxygen sen-
sor connector
 Poor contact in
rear oxygen sen-
sor connector
 Poor contact in
coupling connector
7 CHECK REAR OXYGEN SENSOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between rear oxy-
gen (A/F) sensor connector terminals.
Te r m i n a l s
No. 1 — No. 2:Is the resistance less than 30
Ω?Repair harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
rear oxygen sen-
sor and ECM con-
nector
 Poor contact in
rear oxygen sen-
sor connector
 Poor contact in
ECM connector.
 Poor contact in
coupling connectorReplace the rear
oxygen sensor.
FU(H4SO)-42,
Rear Oxygen Sen-
sor.> Step Check Yes No

EN(H4SO)-88
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
E: DTC P0038 HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Two consecutive driving cycles with fault
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode ERATION, Clear Memory Mode.> and Inspection Mode tion Mode.>.
WIRING DIAGRAM:
EN-02385
BATTERYB61F44
7
B47 MAIN RELAY
12
35
46
B61
12345678
C4B14B19D15
C16C5
REAR
OXYGEN SENSOR
ECM
1432
8B21
B122
T6
E2
B47
T6B21
12 34
56 78
9
10 11 12
13 14 15 16
3456
12
1
B135 B:
D:
B137
SBF-5
C:B136
B122 : LHDB122 : RHDB137
4
1
53
2618 15 167891011
17 19
20121314
B135
567
82
94
310
24 22 23 251112131415
26 27
281617181920 21
B136
5
2
84
3923 20 211011
221617
24
2512136
261915
14
1
7
18
LHD
LHD
RHD
RHD1 8
4
143
T5
B19
2
B19T5
B122
T5
34
12
LHDLHD
RHDRHD
1234
123456781234
B:
D:C:

EN(H4SO)-89
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK INPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 4 (+) — Chassis ground (
−):Is the voltage more than 8 V? Go to step 2.Go to step 3.
2 CHECK CURRENT DATA.
1) Turn the ignition switch to OFF.
2) Repair battery short circuit in harness
between ECM and rear oxygen sensor con-
nector.
3) Turn the ignition switch to ON.
4) Read the data of rear oxygen (A/F) sensor
heater current 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 current more than 7 A? Replace the ECM.
FU(H4SO)-44,
Engine Control
Module (ECM).>END.
3 CHECK POOR CONTACT.
Check poor contact in ECM connector. Is there poor contact in ECM
connector?Repair the poor
contact in ECM
connector.END.

EN(H4SO)-90
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
F: DTC P0068 MANIFOLD PRESSURE SENSOR RANGE/PERFORMANCE
DTC DETECTING CONDITION:
Two consecutive driving cycles with fault
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode ERATION, Clear Memory Mode.> and Inspection Mode tion Mode.>.
WIRING DIAGRAM:
193
15
PRESSURE
SENSOR
9
15 12B22
E3
123E21
E21
ECM
B22
125678
131415169101112
34
17181920
B135
B122
1
2
132
EN-02386
B135
567
82 1
94
310
24 22 23 251112131415
26 27
281617181920 21
B122 : LHD
12345678
B122 : RHD
1234

EN(H4SO)-91
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 DTC using
“List of Diagnostic
Trouble Code
(DTC)”. EN(H4SO)-72, List
of Diagnostic Trou-
ble Code (DTC).>Go to step 2.
2 CHECK AIR INTAKE SYSTEM.Are there holes, loose bolts or
disconnection of hose on air
intake system?Repair air intake
system.Go to step 3.
3 CHECK PRESSURE SENSOR.
1) Start and warm-up the engine until engine
coolant temperature is greater than 60°C
(140°F).
2) Shift the select lever in the “P” or “N” range.
3) Turn the A/C switch to OFF.
4) Turn all accessory switches to OFF.
5) Read the data of manifold absolute pres-
sure sensor signal using Subaru Select Moni-
tor 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 measured value at Igni-
tion ON: 73.3 — 106.6 kPa
(550 — 800 mmHg, 21.65 —
31.50 inHg) Idling: 20.0 — 46.7
kPa (150 — 310 mmHg, 5.91
— 12.20 inHg)?Go to step 4.Replace the mani-
fold absolute pres-
sure sensor. to FU(H4SO)-31,
Manifold Absolute
Pressure Sensor.>
4 CHECK THROTTLE POSITION.
Read the data of throttle position signal using
Subaru Select Monitor or OBD-II general scan
tool.
NOTE:
 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 value less than 5% when
the throttle fully closed?Go to step 5.Adjust or replace
the throttle posi-
tion sensor. to FU(H4SO)-29,
Throttle Position
Sensor.>
5 CHECK THROTTLE POSITION.Is the value more than 85%
when the throttle fully opens?Replace the mani-
fold absolute pres-
sure sensor. to FU(H4SO)-31,
Manifold Absolute
Pressure Sensor.>Replace the throt-
tle position sen-
sor. FU(H4SO)-29,
Throttle Position
Sensor.>

EN(H4SO)-92
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
G: DTC P0107 MANIFOLD ABSOLUTE PRESSURE/BAROMETRIC PRESSURE
CIRCUIT LOW INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode ERATION, Clear Memory Mode.> and Inspection Mode tion Mode.>.
WIRING DIAGRAM:
193
15
PRESSURE
SENSOR
9
15 12B22
E3
123E21
E21
ECM
B22
125678
131415169101112
34
17181920
B135
B122
1
2
132
EN-02386
B135
567
82 1
94
310
24 22 23 251112131415
26 27
281617181920 21
B122 : LHD
12345678
B122 : RHD
1234