2004 SUBARU FORESTER sensor

EN(H4DOTC)-136
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 ON.
2) Disconnect the connector from front oxygen
(A/F) sensor.
3) Measure the voltage of harness between
ECM connector and chassis ground.
Connector & terminal
(B134) No. 26 (+) — Chassis ground (
−):
(B134) No. 33 (+) — Chassis ground (
−):Is the voltage more than 8 V? Replace the front
oxygen (A/F) sen-
sor. FU(H4DOTC)-45,
Front Oxygen (A/
F) Sensor.>Repair the battery
short circuit in har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.

EN(H4DOTC)-137
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Z: DTC P0133 O2 SENSOR CIRCUIT SLOW RESPONSE (BANK 1 SENSOR 1)
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 .
WIRING DIAGRAM:
EN-02320
BATTERYMAIN RELAYSBF-5
B47 1 2 3 5 4 6
E
E
B100F2
14LHD
RHD
LHD
RHD
B100
F2
F60
E3
20
3
RHD
RHD6
72
3
33
26
25
ECMB134
: LHD: LHD
B21: RHD: RHD
1
4 2
3
B262
FRONT OXYGEN
(A/F) SENSOR
3412
56
123
4
56
78
9
1011 12
1314 15 16
B21
F60
B47
B262
B134
F2
LHD LHD
1234
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
1234 5678910 11 12 13 14 15 16 17 18 19 20
: LHDE2: RHD

EN(H4DOTC)-138
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 rele-
vant DTC using
“List of Diagnostic
Trouble Code
(DTC)”. EN(H4DOTC)-74,
List of Diagnostic
Trouble Code
(DTC).>
N
OTE:
In this case, it is
not necessary to
inspect DTC
P0133.Go to step 2.
2 CHECK EXHAUST SYSTEM.
N
OTE:
Check the following items:
 Loose installation of front portion of exhaust
pipe onto cylinder heads
 Loose connection between front exhaust
pipe and front catalytic converter
 Damage of exhaust pipe resulting in a holeIs there a fault in exhaust sys-
tem?Repair exhaust
system.Replace the front
oxygen (A/F) sen-
sor. FU(H4DOTC)-45,
Front Oxygen (A/
F) Sensor.>

EN(H4DOTC)-139
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
AA:DTC P0134 O2 SENSOR CIRCUIT NO ACTIVITY DETECTED (BANK 1 SEN-
SOR 1)
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 spection Mode.>.
WIRING DIAGRAM:
EN-02320
BATTERYMAIN RELAYSBF-5
B47 1 2 3 5 4 6
E
E
B100F2
14LHD
RHD
LHD
RHD
B100
F2
F60
E3
20
3
RHD
RHD6
72
3
33
26
25
ECMB134
: LHD: LHD
B21: RHD: RHD
1
4 2
3
B262
FRONT OXYGEN
(A/F) SENSOR
3412
56
123
4
56
78
9
1011 12
1314 15 16
B21
F60
B47
B262
B134
F2
LHD LHD
1234
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
1234 5678910 11 12 13 14 15 16 17 18 19 20
: LHDE2: RHD

EN(H4DOTC)-140
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 rele-
vant DTC using
“List of Diagnostic
Trouble Code
(DTC)”. EN(H4DOTC)-74,
List of Diagnostic
Trouble Code
(DTC).>Go to step 2.
2 CHECK FRONT (A/F) OXYGEN SENSOR DA-
TA.
1) Start the engine.
2) While observing the Subaru Select Monitor
or OBD-II general scan tool screen, warm-up
the engine until coolant temperature is above
70°C (158°F).
If the engine is already warmed-up, operate at
idle speed for at least 1 minute.
3) Read the data of front oxygen (A/F) 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(H4DOTC)-33, Subaru Select Monitor.>
 OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Instruction Manual.Is the measured value 0.85 —
1.15 (in idling)?Go to step 3.Go to step 4.
3 CHECK REAR OXYGEN SENSOR SIGNAL.
1) Race the engine at speeds from idling to
5,000 rpm for a total of 5 cycles.
N
OTE:
To increase the engine speed to 5,000 rpm,
slowly depress accelerator pedal, taking ap-
prox. 5 seconds, and quickly release accelera-
tor pedal to decrease engine speed.
2) Operate the LED operation mode for
engine.
N
OTE:
 Subaru Select Monitor
For detailed operation procedure, refer to the
“LED OPERATION MODE FOR ENGINE”.
itor.>Does the LED of {Rear O
2 Rich
Signal} blink?Repair the poor
contact in front
oxygen (A/F) sen-
sor and rear oxy-
gen sensor
connector.Check the rear
oxygen sensor cir-
cuit. FU(H4DOTC)-47,
Rear Oxygen Sen-
sor.>
4 CHECK EXHAUST SYSTEM.
Check the exhaust system parts.
NOTE:
Check the following items.
 Loose installation of portions
 Damage (crack, hole etc.) of parts
 Looseness of front oxygen (A/F) sensor
 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 ts.Replace the front
oxygen (A/F) sen-
sor. FU(H4DOTC)-45,
Front Oxygen (A/
F) Sensor.>

EN(H4DOTC)-141
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
AB:DTC P0137 O2 SENSOR CIRCUIT LOW 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 .
WIRING DIAGRAM:
MAIN RELAY
B47 1 2 3 5 4 6
E
T5
*1
*2 B18
3
B122
1
3
T6 REAR
OXYGEN SENSOR
A6
A7D31
C35
ECMB135
B136 B :
B134 A :
C :
1
4
B83
B2 D25
B137D :
EN-02321
: LHD
: RHD34
12
56
B21
B134
B135
F60
B83
B47T6
B1361
23456
F2
2143
LHD : 5
RHD : 4
LHD : 1
RHD : 1*1
*2
BATTERY
B100F2 14LHD
RHD
LHD
RHD LHD
RHD
LHD
RHD 4
6
E
B100
F2
F60
E3
20 3
RHD
LHD
RHD
: LHD
B21: RHD
LHD
: LHDE2
: RHD
B18
B122
B137
2345 678911 12 13 14 17 18 19 201101516
567
82 1
94 310
22 23 11 12 13 14 15
24 25
2616 17
18 19 20 21
27 28 29 30 31
56
782 1
94 310
24 22 23 2511 12 13
1415
26 27
2816
17 18 19 20 21
33 34 29
32 30
31 35
12345678
567
82 1
94 310
24 22 23 2511 12 13 14 15
26 27
2816 17 18 19
20 21
29 30 31 32 33 34 35
123
4
56
78
9
1011 12
1314 15 16
1234
4
22
T5
B18
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

EN(H4DOTC)-142
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(H4DOTC)-74,
List of Diagnostic
Trouble Code
(DTC).>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 keep
the engine speed at 2,000 rpm to 3,000 rpm for
two minutes.
2) Read the data of rear oxygen (A/F) sensor
signal using Subaru Select Monitor or 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”. 33, Subaru Select Monitor.>
 OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.Does the value fluctuate? Go to step 6.Go to step 3.
3 CHECK REAR OXYGEN SENSOR DATA.
Read the data of rear oxygen (A/F) sensor sig-
nal using Subaru Select Monitor or OBD-II
general scan tool.Is the voltage 0.2 — 0.4 V? Go to step 4.Replace the rear
oxygen sensor.
FU(H4DOTC)-47,
Rear Oxygen Sen-
sor.>
4 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
(B137) No. 25 — (T6) No. 4:Is the resistance more than 3
Ω?Repair battery
short circuit in har-
ness between
ECM and rear oxy-
gen sensor con-
nector.Go to step 5.
5 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 engine ground
or chassis ground.
Connector & terminal
(T6) No. 4 (+) — Engine ground (
−):Is the voltage more than 0.2 V? Replace the rear
oxygen sensor.
FU(H4DOTC)-47,
Rear Oxygen Sen-
sor.>Repair the har-
ness and connec-
tor.
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.

EN(H4DOTC)-143
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
6 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(H4DOTC)-47,
Rear Oxygen Sen-
sor.> Step Check Yes No