2004 SUBARU FORESTER engine

EN(H4DOTC 2.5)-69
ENGINE (DIAGNOSTIC)
List of Diagnostic Trouble Code (DTC)
P2101 Throttle Actuator Control Motor Cir-
cuit Range/Performance TROL MOTOR CIRCUIT RANGE/PERFORMANCE, Diagnostic Procedure
with Diagnostic Trouble Code (DTC).>
P2102 Throttle Actuator Control Motor Cir-
cuit Low TROL MOTOR CIRCUIT LOW, Diagnostic Procedure with Diagnostic Trou-
ble Code (DTC).>
P2103 Throttle Actuator Control Motor Cir-
cuit High TROL MOTOR CIRCUIT HIGH, Diagnostic Procedure with Diagnostic Trou-
ble Code (DTC).>
P2109 Throttle/Pedal Position Sensor A
Minimum Stop Performance SENSOR A MINIMUM STOP PERFORMANCE, Diagnostic Procedure with
Diagnostic Trouble Code (DTC).>
P2122 Throttle/Pedal Position Sensor/
Switch “D” Circuit Low Input SENSOR/SWITCH “D” CIRCUIT LOW INPUT, Diagnostic Procedure with
Diagnostic Trouble Code (DTC).>
P2123 Throttle/Pedal Position Sensor/
Switch “D” Circuit High Input SENSOR/SWITCH “D” CIRCUIT HIGH INPUT, Diagnostic Procedure with
Diagnostic Trouble Code (DTC).>
P2127 Throttle/Pedal Position Sensor/
Switch “E” Circuit Low Input SENSOR/SWITCH “E” CIRCUIT LOW INPUT, Diagnostic Procedure with
Diagnostic Trouble Code (DTC).>
P2128 Throttle/Pedal Position Sensor/
Switch “E” Circuit High Input SENSOR/SWITCH “E” CIRCUIT HIGH INPUT, Diagnostic Procedure with
Diagnostic Trouble Code (DTC).>
P2135 Throttle/Pedal Position Sensor/
Switch “A”/“B” Voltage Rationality SENSOR/SWITCH “A”/“B” VOLTAGE RATIONALITY, Diagnostic Procedure
with Diagnostic Trouble Code (DTC).>
P2138 Throttle/Pedal Position Sensor/
Switch “D”/“E” Voltage Rationality SENSOR/SWITCH “D”/“E” VOLTAGE RATIONALITY, Diagnostic Procedure
with Diagnostic Trouble Code (DTC).> DTC Item NOTE

EN(H4DOTC 2.5)-70
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
18.Diagnostic Procedure with Diagnostic Trouble Code (DTC)
A: DTC P0031 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Immediately at fault recognition.
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode OPERATION, Clear Memory Mode.> and Inspection Mode 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)-71
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK POWER SUPPLY TO FRONT OXY-
GEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from front oxygen
(A/F) sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between front oxygen
(A/F) sensor connector and engine ground.
Connector & terminal
(B262) No. 1 (+) — Engine ground (
−):Is the voltage more than 10 V? Go to step 2.Repair the power
supply line.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
main relay and
front oxygen (A/F)
sensor connector
 Poor contact in
front oxygen (A/F)
sensor connector
 Poor contact in
main relay connec-
tor
2 CHECK GROUND CIRCUIT FOR ECM.
Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B134) No. 6 — Chassis ground:
(B134) No. 7 — Chassis ground:Is the resistance less than 5
Ω?Go to step 3.Repair the harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
ECM and engine
ground cable
 Poor contact in
ECM connector.
 Poor contact in
coupling connector
3 CHECK CURRENT DATA.
1) Start the engine.
2) 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
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. 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 current more than 0.2 A? Repair poor con-
tact connector.
N
OTE:
In this case repair
the following:
 Poor contact in
front oxygen (A/F)
sensor connector
 Poor contact in
ECM connector.Go to step 4.
4 CHECK OUTPUT SIGNAL FROM ECM.
1) Start and idle the engine.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 2 (+) — Chassis ground (
−):
(B134) No. 3 (+) — Chassis ground (
−):Is the voltage less than 1 V? Go to step 6.Go to step 5.
5 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B134) No. 2 (+) — Chassis ground (
−):
(B134) No. 3 (+) — Chassis ground (
−):Does the voltage change by
shaking the harness and con-
nector of ECM while monitor-
ing the value with voltage
meter?Repair the poor
contact in ECM
connector.Go to step 6.

EN(H4DOTC 2.5)-72
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
6 CHECK FRONT OXYGEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between front oxy-
gen (A/F) sensor connector terminals.
Te r m i n a l s
No. 1 — No. 2:Is the resistance less than 10
Ω?Repair the harness
and connector.
N
OTE:
In this case repair
the following:
 Open or ground
short circuit in har-
ness between front
oxygen (A/F) sen-
sor and ECM con-
nector
 Poor contact in
front oxygen (A/F)
sensor connector
 Poor contact in
ECM connector.Replace the front
oxygen (A/F) sen-
sor. FU(H4DOTC 2.5)-
36, Front Oxygen
(A/F) Sensor.> Step Check Yes No

EN(H4DOTC 2.5)-73
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
B: 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 OPERATION, Clear Memory Mode.> and Inspection Mode 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)-74
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
(B134) No. 2 (+) — Chassis ground (
−):
(B134) No. 3 (+) — Chassis ground (
−):Is the voltage more than 8 V? Go to step 3.Go to step 2.
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
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. 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 current more than 2.3 A? Replace the ECM.
FU(H4DOTC 2.5)-
41, Engine Con-
trol Module
(ECM).>END.
3 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B134) No. 2 (+) — Chassis ground (
−):
(B134) No. 3 (+) — Chassis ground (
−):Does the voltage change by
shaking the harness and con-
nector of ECM while monitor-
ing the value with voltage
meter?Repair battery
short circuit in har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.END.

EN(H4DOTC 2.5)-75
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
C: DTC P0037 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode OPERATION, Clear Memory Mode.> and Inspection Mode Inspection Mode.>.
WIRING DIAGRAM:
EN-02360
B122 B47 1 2 3 5 4 6
E
E
B21
E23
4
1
B122
34 12
56123
4
56
78
9
1011 12
1314 15 16
: B134
: B135B21
B47 T6
: B136 T6
A6
A7B2
D25
D31
C35
C : B :
D :
4
6
B83A
B
C
B136
B137 B135 B134 A :
: B137
D
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
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
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
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
ECM MAIN RELAYBATTERY
REAR OXYGEN
SENSOR
12345678
B18 T52
B18
T5
B18
1234
B83
1
23456
1234
3 1
4
1
2
4
3

EN(H4DOTC 2.5)-76
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
(B134) No. 6 — Chassis ground:
(B134) No. 7 — Chassis ground:Is the resistance less than 5
Ω?Go to step 2.Repair the har-
ness and connec-
tor.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
ECM and engine
ground cable
 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.
NOTE:
 Subaru Select Monitor
For detailed operation procedure, refer to
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. 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 current more than 0.2 A? Repair the connec-
tor.
NOTE:
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
(B135) No. 2 (+) — 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
(B135) No. 2 (+) — Chassis ground (
−):Does the voltage change by
shaking the harness and con-
nector of ECM while monitor-
ing the value with voltage
meter?Repair the poor
contact in ECM
connector.Go to step 5.
5 CHECK OUTPUT SIGNAL FROM ECM.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from rear oxygen
sensor.
3) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 2 (+) — Chassis ground (
−):Is the voltage less than 1 V? Replace the ECM.
FU(H4DOTC 2.5)-
41, Engine Con-
trol Module
(ECM).>Repair battery short
circuit in harness
between ECM and
rear oxygen sensor
connector. After
repair, replace the
ECM. FU(H4DOTC 2.5)-
41, Engine Con-
trol Module
(ECM).>