2004 SUBARU FORESTER check engine

EN(H4DOTC 2.5)-88
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
2 CHECK INPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 16 (+) — 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.Contact the SUB-
ARU dealer.
N
OTE:
Inspection by DTM
is required, because
probable cause is
deterioration of mul-
tiple parts.
3 CHECK INPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 22 (+) — Chassis ground (
−):Is the voltage more than 4.5 V? Go to step 4.Contact the SUB-
ARU dealer.
N
OTE:
Inspection by DTM
is required, because
probable cause is
deterioration of mul-
tiple parts.
4 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the manifold
absolute pressure sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between manifold
absolute pressure sensor connector and
engine ground.
Connector & terminal
(E21) No. 3 (+) — Engine ground (
−):Is the voltage more than 4.5 V? Go to step 5.Repair the open
circuit in harness
between ECM and
manifold absolute
pressure sensor
connector.
5 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM and manifold absolute pressure
sensor connector.
Connector & terminal
(B136) No. 22 — (E21) No. 1:Is the resistance less than 1
Ω?Go to step 6.Repair the open
circuit in harness
between ECM and
manifold absolute
pressure sensor
connector.
6 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
Measure the resistance of harness between
ECM and manifold absolute pressure sensor
connector.
Connector & terminal
(B136) No. 35 — (E21) No. 2:Is the resistance less than 1
Ω?Go to step 7.Repair the open
circuit in harness
between ECM and
manifold absolute
pressure sensor
connector.
7 CHECK POOR CONTACT.
Check poor contact in manifold absolute pres-
sure sensor connector.Is there poor contact in mani-
fold absolute pressure sensor
connector?Repair poor con-
tact in manifold
absolute pressure
sensor connector.Replace the mani-
fold absolute pres-
sure sensor. to FU(H4DOTC
2.5)-31, Manifold
Absolute Pres-
sure Sensor.> Step Check Yes No

EN(H4DOTC 2.5)-90
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 intake air temperature
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”. 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 engine coolant temperature
more than 55°C (131°F)?Go to step 2.Repair the poor
contact.
N
OTE:
In this case repair
the following:
 Poor contact in
mass air flow and
intake air tempera-
ture sensor
 Poor contact in
ECM
 Poor contact in
joint connector
2 CHECK HARNESS BETWEEN MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from mass air
flow and intake air temperature sensor.
3) Turn the ignition switch to ON.
4) Read the data of intake air temperature
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”. 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 −36°C
(−33°F)?Replace the mass
air flow and intake
air temperature
sensor. FU(H4DOTC 2.5)-
30, Mass Air Flow
and Intake Air
Temperature Sen-
sor.>Repair ground
short circuit in har-
ness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector.

EN(H4DOTC 2.5)-92
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 intake air temperature
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”. 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 −36°C
(−33°F)?Go to step 2.Repair the poor
contact.
N
OTE:
In this case repair
the following:
 Poor contact in
mass air flow and
intake air tempera-
ture sensor
 Poor contact in
ECM
 Poor contact in
joint connector
2 CHECK HARNESS BETWEEN MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from mass air
flow and intake air temperature sensor.
3) Measure the voltage between mass air flow
and intake air temperature sensor connector
and engine ground.
Connector & terminal
(B3) No. 4 (+) — Engine ground (
−):Is the voltage more than 10 V? Repair the battery
short circuit in har-
ness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector.Go to step 3.
3 CHECK HARNESS BETWEEN MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between mass air flow
and intake air temperature sensor connector
and engine ground.
Connector & terminal
(B3) No. 4 (+) — Engine ground (
−):Is the voltage more than 10 V? Repair the battery
short circuit in har-
ness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector.Go to step 4.
4 CHECK HARNESS BETWEEN MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR AND ECM CONNECTOR.
Measure the voltage between mass air flow
and intake air temperature sensor and mani-
fold absolute pressure sensor connector and
engine ground.
Connector & terminal
(B3) No. 4 (+) — Engine ground (
−):Is the voltage more than 4 V? Go to step 5.Repair the harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector
 Poor contact in
mass air flow and
intake air tempera-
ture sensor
 Poor contact in
ECM
 Poor contact in
joint connector

EN(H4DOTC 2.5)-93
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
5 CHECK HARNESS BETWEEN MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness
between mass air flow and intake air tempera-
ture sensor and engine ground.
Connector & terminal
(B3) No. 5 — Engine ground:Is the resistance less than 5
Ω?Replace the mass
air flow and intake
air temperature
sensor. FU(H4DOTC 2.5)-
30, Mass Air Flow
and Intake Air
Temperature Sen-
sor.>Repair the harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
mass air flow and
intake air tempera-
ture sensor and
ECM connector
 Poor contact in
mass air flow and
intake air tempera-
ture sensor
 Poor contact in
ECM
 Poor contact in
joint connector Step Check Yes No

EN(H4DOTC 2.5)-95
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”. 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 engine coolant temperature
more than 120°C (248°F)?Go to step 2.Repair the poor
contact.
N
OTE:
In this case repair
the following:
 Poor contact in
engine coolant
temperature sen-
sor
 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) Turn the ignition switch to ON.
4) Read the data of engine coolant tempera-
ture sensor signal using Subaru Select Monitor
or the 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 temperature more than
−40°C (−40°F)?Replace the engine
coolant tempera-
ture sensor. to FU(H4DOTC
2.5)-26, Engine
Coolant Tempera-
ture Sensor.>Repair ground short
circuit in harness
between engine
coolant tempera-
ture sensor and
ECM connector.

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”. 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. 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)-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.
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.
FU(H4DOTC 2.5)-
41, Engine Con-
trol Module
(ECM).>