2004 SUBARU FORESTER sensor

EN(H4SO)-134
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Y: DTC P0138 O2 SENSOR CIRCUIT HIGH VOLTAGE (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)-135
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
using “List of Diag-
nostic Trouble
Code (DTC)”.
EN(H4SO)-72, List
of Diagnostic Trou-
ble Code (DTC).>
N
OTE:
In this case, it is not
necessary to in-
spect DTC P0138.Go to step 2.
2 CHECK REAR OXYGEN SENSOR DATA.
1) Warm-up the engine until engine coolant
temperature is above 70°C (158°F), and lower
the engine speed rapidly from 5,000 rpm.
2) Read the data of rear oxygen (A/F) sensor
signal using Subaru Select Monitor or OBD-II
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 scan tool
For detailed operation procedures, refer to the
OBD-II Scan Tool Instruction Manual.Does the voltage vary from 250
mV?Go to step 5.Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance in harness
between ECM and rear oxygen sensor con-
nector.
Connector & terminal
(B135) No. 14 — (T6) No. 4:
(B135) No. 19 — (T6) No. 3:Is the resistance more than 3
Ω?Repair open circuit
in harness
between ECM and
rear oxygen sen-
sor connector.Go to step 4.
4 CHECK HARNESS BETWEEN REAR OXY-
GEN SENSOR AND ECM CONNECTOR.
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 harness connector and chassis ground.
Connector & terminal
(T6) No. 4 (+) — Chassis ground (
−):Is the voltage 0.2 — 0.5 V? Replace the rear
oxygen sensor.
FU(H4SO)-40,
Front Oxygen (A/
F) Sensor.>Repair harness
and connector.
NOTE:
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.

EN(H4SO)-136
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
5 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
N
OTE:
Check the following items:
 Loose part of exhaust system and incom-
plete installation
 Damage (crack, hole etc.) of parts
 Looseness and ill fitting of parts between
front oxygen (A/F) sensor and rear oxygen
sensorIs there a fault in exhaust sys-
tem?Repair or replace
the faulty par t.Replace the rear
oxygen sensor.
FU(H4SO)-40,
Front Oxygen (A/
F) Sensor.> Step Check Yes No

EN(H4SO)-137
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Z: DTC P0139 O2 SENSOR CIRCUIT SLOW RESPONSE (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)-138
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
AA:DTC P0171 SYSTEM TOO LEAN (BANK 1)
Refer to DTC P0172 for diagnostic procedure. (BANK 1), 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
using “List of Diag-
nostic Trouble
Code (DTC)”.
EN(H4SO)-72, List
of Diagnostic Trou-
ble Code (DTC).>
N
OTE:
In this case, it is not
necessary to in-
spect DTC P0139.Replace the rear
oxygen sensor.
FU(H4SO)-42,
Rear Oxygen Sen-
sor.>

EN(H4SO)-140
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
7 CHECK FUEL PRESSURE.
After connecting the pressure regulator vac-
uum hose, measure fuel pressure.
Warning:
Release fuel pressure before removing the
fuel pressure gauge.
N
OTE:
 If fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure
fuel pressure again.
 If out of specification as measured at this
step, check or replace pressure regulator and
pressure regulator vacuum hose.Is measured value 206 — 235
kPa (2.1 — 2.4 kg/cm
2, 30 —
34 psi)?Go to step 8.Repair the follow-
ing items.
Fuel pressure is
too high:
 Faulty pres-
sure regulator
 Clogged fuel
return line or
bent hose
Fuel pressure is
too low:
 Faulty pres-
sure regulator
 Improper fuel
pump discharge
 Clogged fuel
supply line
8 CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm-up completely.
2) Read the data of engine coolant tempera-
ture sensor signal using Subaru Select Monitor
or the OBD-II 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 scan tool
For detailed operation procedures, refer to the
OBD-II Scan Tool Instruction Manual.Is the engine coolant tempera-
ture 70 — 100°C (158 —
212°F)?Go to step 9.Replace the
engine coolant
temperature sen-
sor. FU(H4SO)-25,
Engine Coolant
Temperature Sen-
sor.>
9 CHECK MANIFOLD PRESSURE SENSOR
SIGNAL.
1) Start and warm-up the engine until engine
coolant temperature is greater than 60°C
(140°F).
2) Shift the select lever to “N” or “P” 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 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 scan tool
For detailed operation procedures, refer to the
OBD-II Scan Tool Instruction Manual.Is the measurement value at
idling: 24.0 — 41.3 kPa (180 —
310 mmHg, 7.09 — 12.20
inHg), at ignition ON: 73.3 —
106.6 kPa (550 — 800 mmHg,
21.65 — 31.50 inHg)?Contact the SUB-
ARU dealer.
NOTE:
Inspection by DTM
is required,
because probable
cause is deteriora-
tion of multiple
parts.Replace the mani-
fold absolute pres-
sure sensor. to FU(H4SO)-31,
Manifold Absolute
Pressure Sensor.> Step Check Yes No

EN(H4SO)-144
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
6 CHECK POWER SUPPLY LINE.
1) Turn the ignition switch to ON.
2) Measure the voltage between fuel injector
and engine ground on faulty cylinders.
Connector & terminal
#1 (E5) No. 2 (+) — Engine ground (
−):
#2 (E16) No. 2 (+) — Engine ground (
−):
#3 (E6) No. 2 (+) — Engine ground (
−):
#4 (E17) No. 2 (+) — Engine ground (
−):Is the voltage more than 10 V? Repair poor con-
tact in all connec-
tors in fuel injector
circuit.Repair harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
main relay and fuel
injector connector
on faulty cylinders
 Poor contact in
coupling connector
 Poor contact in
main relay connec-
tor
 Poor contact in
fuel injector con-
nector on faulty
cylinders
7 CHECK HARNESS BETWEEN FUEL INJEC-
TOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector
on faulty cylinder.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM con-
nector and chassis ground on faulty cylinders.
Connector & terminal
#1 (B134) No. 34 (+) — Chassis ground (
−):
#2 (B134) No. 23 (+) — Chassis ground (
−):
#3 (B134) No. 22 (+) — Chassis ground (
−):
#4 (B134) No. 8 (+) — Chassis ground (
−):Is the voltage more than 10 V? Repair battery
short circuit in har-
ness between
ECM and fuel
injector. After
repair, replace the
ECM. FU(H4SO)-44,
Engine Control
Module (ECM).>Go to step 8.
8 CHECK FUEL INJECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between fuel injec-
tor terminals on faulty cylinder.
Te r m i n a l s
No. 1 — No. 2:Is the resistance less than 1
Ω?Replace the faulty
fuel injector to FU(H4SO)-35,
Fuel Injector.> and
ECM. FU(H4SO)-44,
Engine Control
Module (ECM).>Go to step 9.
9 CHECK INSTALLATION OF CAMSHAFT PO-
SITION SENSOR/CRANKSHAFT POSITION
SENSOR.Is the installation of camshaft
position sensor or crankshaft
position sensor loosened?Tighten camshaft
position sensor or
crankshaft posi-
tion sensor.Go to step 10.
10 CHECK CRANK SPROCKET.
Remove the timing belt cover.Is the crank sprocket rusted or
does it have broken teeth?Replace the crank
sprocket. ME(H4SO)-55,
Crank Sprocket.>Go to step 11.
11 CHECK INSTALLATION CONDITION OF
TIMING BELT.
Turn the crankshaft using ST, and align align-
ment mark on crank sprocket with alignment
mark on cylinder block.
ST 499987500 CRANKSHAFT SOCKETIs the timing belt dislocated
from its proper position?Repair installation
condition of timing
belt. ME(H4SO)-48,
Timing Belt.>Go to step 12.
12 CHECK FUEL LEVEL.Is the fuel meter indication
higher than the “Lower” level?Go to step 13.Replenish fuel so
fuel meter indica-
tion is higher than
the “Lower” level.
After replenishing
fuel, Go to step 13. Step Check Yes No

EN(H4SO)-148
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
AG:DTC P0327 KNOCK SENSOR 1 CIRCUIT LOW INPUT (BANK 1 OR SINGLE
SENSOR)
DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
 Poor driving performance
 Knocking 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-00272
1627
KNOCK
SENSOR
16
2
ECM B135
B22
E3
E14
E14
12
B22
125678
131415169101112
34
17181920
B135
567
82 1
94
310
24 22 23 251112131415
26 27
281617181920 21