2004 SUBARU FORESTER check engine light

4AT(H4DOTC)-23
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Power Indicator Light Display
 RHD model
Step Check Yes No
1 CHECK POWER INDICATOR LIGHT.
Turn the ignition switch to ON (engine OFF).Does the POWER indicator
light illuminate?Go to step 3.Go to step 2.
2 CHECK POWER INDICATOR LIGHT.
1) Turn the ignition switch to OFF.
2) Remove the combination meter.
3) Remove the POWER indicator light bulb
from combination meter.Is the POWER indicator light
bulb OK?Go to step 4.Replace the
POWER indicator
light bulb.
3 CHECK FUSE (No. 14).
Remove the fuse (No. 14).Is the fuse (No. 14) blown out? Replace the fuse
(No. 14). If replaced
fuse (No. 14) is
blown out easily,
repair short circuit
in harness between
fuse (No. 14) and
combination meter.Go to step 4.
AT-01839
TCM
SBF-4 No.14 SBF-1
E
E
A10
A4
A16
B4
B22
B5 B14
C25
P RND3 2 1
9
8
10
3
11
4
6
53
2
1
8
7
6
5
4
T7T7
B12
B55 T3B12
12 34
56 78
9
10
11
12
12 3456
789101112
i10
i11
B9
1116
C2
i2B37
i3B38
POWER
B:
B54 A:B56 C: B:
123456
78 9 10 1112
13
14
15
1617
1819
2021
2223
24
2526
2728
29
30
i10 B: C:
i11
C:
1234
5678910
B56
12 78 956 34
10 11 12 19 20 21
29 30 31 13 14 15 16 17
27 2818
22 23 24 25 26
C:
B55
12 7
8956 34
10 11 12
19 20 2113 14 15 16
17 18 22 23 24
B:
i3
219
32 1234 56
10 11 12 13 14 157
16
23 3019 20
22 26 27 28 298
17
24 3118
25
IGNITION
SWITCH
INHIBITOR SWITCH
BATTERY
CONBINATION
METERB54 A:
123
8910411 12
13 14 15 1656
7
17
i2
123 8
910411 12 13 14 15 165671718

4AT(H4DOTC)-24
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Power Indicator Light Display
4 CHECK HARNESS CONNECTOR BETWEEN
COMBINATION METER AND IGNITION
SWITCH.
1) Turn the ignition switch to ON (engine OFF).
2) Measure the voltage between combination
meter connector and chassis ground.
Connector & terminal
(i10) No. 9 (+) — Chassis ground (
−):Is the voltage more than 9 V? Go to step 5.Repair the open
circuit in harness
between combina-
tion meter and bat-
tery.
5 CHECK COMBINATION METER.
Measure the voltage between combination
meter connector and chassis ground.
Connector & terminal
(i11) No. 2 (+) — Chassis ground (
−):Is the voltage less than 9 V? Repair the combi-
nation meter.
Combination
Meter Assembly.>Go to step 6.
6 CHECK OPEN CIRCUIT OF HARNESS.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from combination
meter connector.
3) Measure the resistance of harness
between combination meter.
Connector & terminal
(B56) No. 25 — (i11) No. 2:Is the resistance less than 1
Ω?Go to step 7.Repair the open
circuit in harness
between TCM and
combination
meter, and poor
contact in cou-
pling connector.
7 CHECK INPUT SIGNAL FOR TCM.
1) Connect the connector to TCM and combi-
nation meter.
2) Turn the ignition switch to ON (engine OFF).
3) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B56) No. 25 (+) — Chassis ground (
−):Is the voltage less than 1 V? Go to step 8.Replace the TCM.
Transmission Con-
trol Module
(TCM).>
8 INSPECT POWER INDICATOR LIGHT.Does the POWER indicator
light illuminate?Diagnose accord-
ing to basic diag-
nostic procedure.Inspect power sup-
ply and ground cir-
cuit. Step Check Yes No

4AT(H4DOTC)-26
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Power Indicator Light Display
2 CHECK POWER SUPPLY OF TCM.
1) Disconnect the connector from TCM.
2) Turn the ignition switch to ON.
3) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B56) No. 27 (+) — Chassis ground (
−):
(B56) No. 28 (+) — Chassis ground (
−):
(B56) No. 29 (+) — Chassis ground (
−):Is the voltage 10 — 13 V? Go to step 4.Go to step 3.
3 CHECK FUSE (No. 4).
1) Turn the ignition switch to OFF.
2) Remove the fuse (No. 4).Is the fuse (No. 4) blown out? Replace the fuse
(No. 4). If replaced
fuse (No. 4) has
blown out easily,
repair short circuit
in harness between
fuse (No. 4) and
TCM.Repair the open
circuit in harness
between fuse (No.
4) and TCM, or
fuse (No. 4) and
battery, and poor
contact in cou-
pling connector.
4 CHECK IGNITION POWER SUPPLY CIR-
CUIT.
1) Turn the ignition switch to ON (engine OFF).
2) Measure the ignition power supply voltage
between TCM connector and chassis ground.
Connector & terminal
(B56) No. 21 (+) — Chassis ground (–):
(B56) No. 31 (+) — Chassis ground (–):Is the voltage 10 — 13 V? Go to step 6.Go to step 5.
5 CHECK FUSE (No. 11).
Remove the fuse (No. 11).Is the fuse (No. 11) blown out? Replace the fuse
(No. 11). If
replaced fuse (No.
11) has blown out
easily, repair short
circuit in harness
between fuse (No.
11) and TCM.Repair the open
circuit in harness
between fuse (No.
11) and TCM, or
fuse (No. 11) and
battery, and poor
contact in cou-
pling connector.
6 CHECK HARNESS CONNECTOR BETWEEN
TCM AND TRANSMISSION.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from TCM and
transmission.
3) Measure the resistance of harness
between TCM and transmission connector.
Connector & terminal
(B55) No. 8 — (B11) No. 19:
(B55) No. 17 — (B11) No. 19:
(B56) No. 2 — (B11) No. 20:
(B56) No. 3 — (B11) No. 20:Is the resistance less than 1
Ω?Go to step 7.Repair the open
circuit in harness
between TCM,
transmission har-
ness connector,
and poor contact
in coupling con-
nector.
7 CHECK HARNESS CONNECTOR BETWEEN
TRANSMISSION AND TRANSMISSION
GROUND.
Measure the resistance of harness between
transmission and transmission ground.
Connector & terminal
(T4) No. 19 — Transmission ground:
(T4) No. 20 — Transmission ground:Is the resistance less than 1
Ω?Go to step 8.Repair the open
circuit in harness
between transmis-
sion and transmis-
sion ground.
8 CHECK POOR CONTACT IN CONNECTORS.Is there poor contact in TCM
power supply, ground line and
data link connector?Repair the con-
nector.Replace the TCM.
Transmission Con-
trol Module
(TCM).> Step Check Yes No

4AT(H4DOTC)-43
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
2 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ATF TEMPERATURE SENSOR.
Measure the resistance of harness between
TCM and transmission connector.
Connector & terminal
(B55) No. 9 — (B11) No. 15:Is the resistance less than 1
Ω?Go to step 3.Repair the open
circuit in harness
between TCM and
transmission con-
nector.
3 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ATF TEMPERATURE SENSOR.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B55) No. 21 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 4.Repair the short
circuit in harness
between TCM and
transmission con-
nector.
4 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ATF TEMPERATURE SENSOR.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B55) No. 9 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 5.Repair the short
circuit in harness
between TCM and
transmission con-
nector.
5 CHECK ATF TEMPERATURE SENSOR.
1) Turn the ignition switch to OFF.
2) Connect the connectors to transmission
and TCM.
3) Turn the ignition switch to ON and start
engine.
4) Warm-up the transmission until ATF tem-
perature reaches to 80°C (176°F).
N
OTE:
If ambient temperature is below 0°C (32°F),
drive the vehicle until ATF reaches its operating
temperature.
5) Disconnect the connector from transmis-
sion.
6) Measure the resistance between transmis-
sion connector terminals.
Connector & terminal
(T4) No. 11 — No. 15:Is the resistance 500 — 600
Ω?Go to step 6.Go to step 11.
6 CHECK ATF TEMPERATURE SENSOR.
Measure the resistance between transmission
connector terminals.
Connector & terminal
(T4) No. 11 — No. 15:Does the resistance value
increase when ATF tempera-
ture decreases?Go to step 7.Go to step 11.
7 PREPARE SUBARU SELECT MONITOR.Do you have a Subaru Select
Monitor?Go to step 9.Go to step 8.
8 CHECK INPUT SIGNAL FOR TCM.
1) Connect the connector to transmission.
2) Warm-up the transmission until ATF tem-
perature is about 80°C (176°F).
N
OTE:
If ambient temperature is below 0°C (32°F),
drive the vehicle until ATF reaches its operating
temperature.
3) Measure the voltage between TCM con-
nector terminal.
Connector & terminal
(B55) No. 9 (+) — No. 21 (
−):Is the voltage 1.5 — 1.9 V? Even if the POWER
indicator light was
blinking the circuit
has returned to a
normal condition at
this time. Tempo-
rary poor contact of
the connector or
harness may be the
cause. Repair the
harness or contact
in ATF temperature
sensor and trans-
mission connector.Go to step 10. Step Check Yes No

4AT(H4DOTC)-44
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
9 CHECK INPUT SIGNAL FOR TCM USING
SUBARU SELECT MONITOR.
1) Connect the connector to transmission.
2) Turn the ignition switch to ON (engine
OFF).
3) Read the data of ATF temperature using the
Subaru Select Monitor. 15, OPERATION, Subaru Select Monitor.>Does the ATF temperature
gradually decrease?Even if the POWER
indicator light was
blinking, the circuit
has returned to a
normal condition at
this time. Tempo-
rary poor contact of
the connector or
harness may be the
cause. Repair the
harness or contact
in ATF temperature
sensor and trans-
mission connector.Go to step 10.
10 CHECK POOR CONTACT.Is there poor contact in ATF
temperature sensor circuit?Repair the poor
contact.Replace the TCM.
Transmission Con-
trol Module
(TCM).>
11 CHECK HARNESS CONNECTOR BETWEEN
TRANSMISSION AND ATF TEMPERATURE
SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from transmis-
sion.
3) Remove the transmission connector from
bracket.
4) Lift-up the vehicle and place rigid racks.
NOTE:
Raise all wheels off floor.
5) Drain the ATF.
CAUTION:
Do not drain the ATF until it cools down.
6) Remove the oil pan, and disconnect the
connector from ATF temperature sensor con-
nector.
7) Measure the resistance of harness
between ATF temperature sensor and trans-
mission connector.
Connector & terminal
(T4) No. 11 — (AT11) No. 1:Is the resistance less than 1
Ω?Go to step 12.Repair the open
circuit in harness
between ATF tem-
perature sensor
and transmission
connector.
12 CHECK HARNESS CONNECTOR BETWEEN
TRANSMISSION AND ATF TEMPERATURE
SENSOR.
Measure the resistance of harness between
ATF temperature sensor and transmission con-
nector.
Connector & terminal
(T4) No. 15 — (AT11) No. 3:Is the resistance less than 1
Ω?Go to step 13.Repair the open
circuit in harness
between ATF tem-
perature sensor
and transmission
connector.
13 CHECK HARNESS CONNECTOR BETWEEN
TRANSMISSION AND ATF TEMPERATURE
SENSOR.
Measure the resistance of harness between
transmission connector and transmission
ground.
Connector & terminal
(T4) No. 11 — Transmission ground:Is the resistance more than 1
MΩ?Go to step 14.Repair the short
circuit in harness
between ATF tem-
perature sensor
and transmission
connector. Step Check Yes No

4AT(H4DOTC)-47
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
2 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ATF TEMPERATURE SENSOR.
Measure the voltage of harness between TCM
connector and chassis ground.
Connector & terminal
(B55) No. 9 (+) — Chassis ground (
−):Is the voltage less than 1 V? Go to step 3.Repair the short
circuit in harness
between TCM and
transmission con-
nector.
3 CHECK ATF TEMPERATURE SENSOR.
1) Turn the ignition switch to OFF.
2) Connect the connectors to transmission
and TCM.
3) Turn the ignition switch to ON and start
engine.
4) Warm-up the transmission until ATF tem-
perature reaches to 80°C (176°F).
N
OTE:
If ambient temperature is below 0°C (32°F),
drive the vehicle until ATF reaches its operating
temperature.
5) Disconnect the connector from transmis-
sion.
6) Measure the resistance between transmis-
sion connector terminals.
Connector & terminal
(T4) No. 11 — No. 15:Is the resistance 500 — 600
Ω?Go to step 4.Replace ATF tem-
perature sensor.
Control Valve
Body.>
4 CHECK ATF TEMPERATURE SENSOR.
Measure the resistance between transmission
connector terminals.
Connector & terminal
(T4) No. 11 — No. 15:Does the resistance value
increase when ATF tempera-
ture decreases? Go to step 5.Replace ATF tem-
perature sensor.
Control Valve
Body.>
5 PREPARE SUBARU SELECT MONITOR.Do you have a Subaru Select
Monitor?Go to step 7.Go to step 6.
6 CHECK INPUT SIGNAL FOR TCM.
1) Connect the connector to transmission.
2) Warm-up the transmission until ATF tem-
perature is about 80°C (176°F).
N
OTE:
If ambient temperature is below 0°C (32°F),
drive the vehicle until ATF reaches its operating
temperature.
3) Measure the voltage between TCM con-
nector terminal.
Connector & terminal
(B55) No. 9 (+) — No. 21 (
−):Is the voltage 1.5 — 1.9 V? Even if the POWER
indicator light was
blinking, the circuit
has returned to a
normal condition at
this time. Tempo-
rary poor contact of
the connector or
harness may be the
cause. Repair the
harness or contact
in ATF temperature
sensor and trans-
mission connector.Go to step 8.
7 CHECK INPUT SIGNAL FOR TCM USING
SUBARU SELECT MONITOR.
1) Connect the connector to transmission.
2) Turn the ignition switch to ON (engine
OFF).
3) Read the data of ATF temperature using
the Subaru Select Monitor. 4AT(H4DOTC)-15, OPERATION, Subaru
Select Monitor.>Does the ATF temperature
gradually decrease?Even if the POWER
indicator light was
blinking, the circuit
has returned to a
normal condition at
this time. Tempo-
rary poor contact of
the connector or
harness may be the
cause. Repair the
harness or contact
in ATF temperature
sensor and trans-
mission connector.Go to step 8. Step Check Yes No

4AT(H4DOTC)-50
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
2 CHECK HARNESS CONNECTOR BETWEEN
TCM AND TRANSMISSION.
1) Disconnect the connector from TCM.
2) Measure the resistance of harness
between TCM and transmission connector.
Connector & terminal
(B55) No. 7 — (B11) No. 5:Is the resistance less than 1
Ω?Go to step 3.Repair the open
circuit in harness
between TCM and
transmission con-
nector.
3 CHECK HARNESS CONNECTOR BETWEEN
TCM AND TRANSMISSION.
Measure the resistance of harness between
TCM and transmission connector.
Connector & terminal
(B55) No. 16 — (B11) No. 10:Is the resistance less than 1
Ω?Go to step 4.Repair the open
circuit in harness
between TCM and
transmission con-
nector, and poor
contact in cou-
pling connector.
4 CHECK HARNESS CONNECTOR BETWEEN
TCM AND TRANSMISSION.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B55) No. 16 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 5.Repair the short
circuit in harness
between TCM and
transmission con-
nector.
5 CHECK HARNESS CONNECTOR BETWEEN
TCM AND TRANSMISSION.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B55) No. 7 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 6.Repair the short
circuit in harness
between TCM and
transmission con-
nector, and poor
contact in cou-
pling connector.
6 PREPARE OSCILLOSCOPE.Do you have an oscilloscope? Go to step 10.Go to step 7.
7 PREPARE SUBARU SELECT MONITOR.Do you have a Subaru Select
Monitor?Go to step 9.Go to step 8.
8 CHECK INPUT SIGNAL FOR TCM.
1) Connect the connectors to TCM and trans-
mission.
2) Start the engine and shift select lever to “P”
or “N” range.
3) Measure the voltage between TCM con-
nector terminals.
Connector & terminal
(B55) No. 7 (+) — No. 16 (
−):Is the voltage more than AC 1
V?Even if the POWER
indicator light was
blinking, the circuit
has returned to a
normal condition at
this time. A tempo-
rary poor contact of
the connector or
harness may be the
cause. Repair the
harness or connec-
tor in TCM and
transmission.Go to step 11.
9 CHECK INPUT SIGNAL FOR TCM USING
SUBARU SELECT MONITOR.
1) Connect the connectors to TCM and trans-
mission.
2) Connect the Subaru Select Monitor to data
link connector.
3) Turn the ignition switch to ON and turn Sub-
aru Select Monitor switch to ON.
4) Start the engine.
5) Shift the select lever to “P” or “N” range.
6) Read the data of turbine speed using Sub-
aru Select Monitor.
 Compare the tachometer with Subaru Select
Monitor indications.Is the revolution value same as
the tachometer reading shown
on the combination meter?Even if the POWER
indicator light was
blinking, the circuit
has returned to a
normal condition at
this time. A tempo-
rary poor contact of
the connector or
harness may be the
cause. Repair the
harness or connec-
tor in TCM and
transmission.Go to step 11. Step Check Yes No

4AT(H4DOTC)-51
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
10 CHECK INPUT SIGNAL FOR TCM USING
OSCILLOSCOPE.
1) Connect the connectors to TCM and trans-
mission.
2) Set the oscilloscope to TCM connector ter-
minals.
Connector & terminal
Positive probe; (B55) No. 7:
Earth lead; (B55) No. 16:
3) Start the engine and move select lever to
“P” or “N” range.Is the voltage more than AC 1
V?Even if the POWER
indicator light was
blinking, the circuit
has returned to a
normal condition at
this time. A tempo-
rary poor contact of
the connector or
harness may be the
cause. Repair the
harness or connec-
tor in TCM and
transmission.Go to step 11.
11 CHECK POOR CONTACT.Is there poor contact in torque
converter turbine speed sensor
circuit?Repair the poor
contact.Replace the TCM.
Transmission Con-
trol Module
(TCM).> Step Check Yes No