2004 SUBARU FORESTER automatic transmission

4AT(H4DOTC)-109
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK HARNESS CONNECTOR BETWEEN
TCM AND THROTTLE POSITION SENSOR
OR ACCELERATOR PEDAL POSITION SEN-
SOR.
1) Disconnect the connector from TCM.
2) Measure the resistance of harness
between TCM and throttle position sensor or
accelerator pedal position sensor connector.
Connector & terminal
2.0 L model
(B55) No. 10 — (E13) No. 1:
2.5 L model
(B55) No. 10 — (B315) No. 1:Is the resistance less than 1
Ω?Go to step 2.Repair the open cir-
cuit in harness
between TCM and
throttle position
sensor or accelera-
tor pedal position
sensor connector,
and poor contact in
coupling connector.
2 CHECK HARNESS CONNECTOR BETWEEN
TCM AND THROTTLE POSITION SENSOR
OR ACCELERATOR PEDAL POSITION SEN-
SOR.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B55) No. 10 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 3.Repair the short
circuit in harness
between TCM and
throttle position
sensor or acceler-
ator pedal position
sensor connector.
3 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ECM.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Measure the voltage of harness between
TCM and chassis ground.
Connector & terminal
(B55) No. 10 (+) — Chassis ground (
−):Is the voltage approx. 5 V? Go to step 4.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 throttle posi-
tion sensor or
accelerator pedal
position sensor cir-
cuit.
4 CHECK POOR CONTACT.Is there poor contact in sensor
circuit?Repair the poor
contact.Replace the TCM.
Transmission Con-
trol Module
(TCM).>

4AT(H4DOTC)-110
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
AA:DTC P1718 CAN COMMUNICATION CIRCUIT
DTC DETECTING CONDITION:
Input signal circuit of TCM is open or shorted.
WIRING DIAGRAM:
Step Check Yes No
1 CHECK DTC.Are multiple DTCs displayed in
the on-board diagnostics test
mode?Go to other DTC. Go to step 2.
2 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ECM.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from TCM and
ECM.
3) Measure the resistance of harness
between TCM and ECM connectors.
Connector & terminal
(B55) No. 3 — (B137) No. 18:Is the resistance less than 1
Ω?Go to step 3.Repair the open
circuit in harness
between TCM and
ECM or poor con-
tact of connector.
AT-01853
1832612
B55
B137
ECM
B55
TCM
B137
12
7
8956 3410 11 12
19 20 2113 14 15 16
17 1822
23
24
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
TWISTED WIRE

4AT(H4DOTC)-111
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
3 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ECM.
Measure the resistance of harness between
TCM and ECM connectors.
Connector & terminal
(B55) No. 12 — (B137) No. 26:Is the resistance less than 1
Ω?Go to step 4.Repair the open
circuit in harness
between TCM and
ECM or poor con-
tact of connector.
4 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ECM.
Measure the resistance of harness between
TCM and chassis ground connectors.
Connector & terminal
(B55) No. 3 — Chassis ground:
(B55) No. 12 — Chassis ground:Is the resistance more than 1
MΩ?There is failure in
the TCM or ECM.
(Replace and
check again)Repair the short
circuit in harness
between TCM and
ECM. Step Check Yes No

4AT(H4DOTC)-112
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure without Diagnostic Trouble Code (DTC)
14.Diagnostic Procedure without Diagnostic Trouble Code (DTC)
A: CHECK FWD SWITCH
DIAGNOSIS:
 The LED does not come on even if FWD switch is ON.
 The FWD signal circuit is open or short.
WIRING DIAGRAM:
 LHD model
AT-01854
BATTERYSBF-4 SBF-1
No.14
IGNITION
SWITCH
FWD
i10
i2
B37
B56TCM
F45
B62
F27
22
9
36
16
35
14
17
COMBINATION
METER
E
E
FWD SWITCH
159i3
B38
123456
78 9 10 1112
13
14
15 16 17
181920
21
2223
24
2526
272829
30
1234
578
910112324
121314
156
16 17 1819
20 2122123 4
57
8
91011
121314
156
16
219
32
B38
1234
5610 11 12 13 14 15716
23 3019 20
22 26 27 28 29817
24 3118
2556789
1011121314
1516171819
2021222324
252627282936
3512
34
3031323334
F27
B56
i10B37F45
12
789 56 3
410 11 1219 20 21
29 30 31 13 14 15 1617
27 2818
22 23 24 25 26

4AT(H4DOTC)-113
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure without Diagnostic Trouble Code (DTC)
 RHD model
AT-01855
BATTERY
123456
78 9 10 1112
13
14
15 16 17
1819
2021
2223
24
2526
2728
2930
SBF-4 SBF-1
No.14
IGNITION
SWITCH
FWDi10
i3
B38
B56TCM
F45
B62
F27
22
9
36
16
35
14
17
COMBINATION
METER
E
E
FWD SWITCH
1234
5678
910
11
121314
1516 17 1819
20 21221234567812
131415
1617 1891011
1
219
32
i3
1234
5610 11 12 13 14 15716
23 3019 20
22 26 27 28 29817
24 3118
25
56789
1011121314
1516171819
2021222324
252627282936
3512
34
3031323334
F27
i10
i2 B56
F45
1615i2
B37
12
789 56 3
410 11 1219 20 21
29 30 31 13 14 15 1617
27 2818
22 23 24 25 26

4AT(H4DOTC)-114
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure without Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK FWD SWITCH.When the fuse is inserted to
FWD switch, does LED light
up?Go to step CHECK
POWER SWITCH.
4AT(H4DOTC)-
116, CHECK
POWER SWITCH,
Diagnostic Proce-
dure without Diag-
nostic Trouble
Code (DTC).>Go to step 2.
2 CHECK FWD INDICATOR LIGHT.
1) Turn the ignition switch to OFF.
2) Remove the combination meter.Is the FWD indicator light bulb
OK?Go to step 3.Check the combi-
nation meter.
Combination
Meter Assembly.>
3 CHECK HARNESS CONNECTOR BETWEEN
TCM AND FWD SWITCH.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from TCM and
FWD switch.
3) Measure the resistance of harness
between TCM and FWD switch connector.
Connector & terminal
(B56) No. 17 — (F27) No. 36:Is the resistance less than 1
Ω?Go to step 4.Repair the open
circuit in harness
between TCM and
FWD switch con-
nector.
4 CHECK HARNESS CONNECTOR BETWEEN
TCM AND FWD SWITCH.
Measure the resistance of harness connector
between TCM and body to make sure that cir-
cuit does not short.
Connector & terminal
(B56) No. 17 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 5.Repair the short
circuit in harness
between TCM and
FWD switch con-
nector.
5 CHECK HARNESS CONNECTOR BETWEEN
FWD SWITCH AND CHASSIS GROUND.
Measure the resistance of harness between
FWD switch and chassis ground.
Connector & terminal
(F27) No. 35 — Chassis ground:Is the resistance less than 1
Ω?Go to step 6.Repair the open
circuit in harness
between FWD
switch connector
and chassis
ground.
6 CHECK INPUT SIGNAL FOR TCM.
1) Turn the ignition switch to OFF.
2) Connect the connector to FWD switch and
TCM.
3) Turn the ignition switch to ON.
4) Measure the signal voltage for TCM while
installing the fuse to FWD switch connector.
Connector & terminal
(B56) No. 17 (+) — Chassis ground (
−):Is the voltage less than 1 V? Go to step 7.Go to step 11.
7 CHECK INPUT SIGNAL FOR TCM.
Measure the signal voltage for TCM while
removing the fuse from FWD switch connector.
Connector & terminal
(B56) No. 17 (+) — Chassis ground (
−):Is the voltage more than 10.5
V?Go to step 8.Replace the TCM.
Transmission Con-
trol Module
(TCM).>
8 CHECK HARNESS CONNECTOR BETWEEN
TCM AND COMBINATION METER.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from TCM and
combination meter.
3) Measure the resistance of harness between
TCM and combination meter connector.
Connector & terminal
(B56) No. 14 — (i10) No. 22:Is the resistance less than 1
Ω?Go to step 9.Repair the open
circuit in harness
between TCM and
combination meter
and poor contact
in coupling con-
nector.

4AT(H4DOTC)-115
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure without Diagnostic Trouble Code (DTC)
9 CHECK HARNESS CONNECTOR BETWEEN
TCM AND COMBINATION METER.
Measure the resistance of harness connector
between TCM and chassis ground to make
sure that circuit does not short.
Connector & terminal
(B56) No. 14 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 10.Repair the short
circuit in harness
between TCM and
combination meter
connector.
10 CHECK OUTPUT SIGNAL EMITTED FROM
TCM.
1) Turn the ignition switch to OFF.
2) Connect the connector to TCM and combi-
nation meter.
3) Turn the ignition switch to ON.
4) Measure the signal voltage for TCM while
installing and removing the fuse to FWD switch
connector.
Connector & terminal
(B56) No. 14 (+) — Chassis ground (
−):Is the voltage less than 1 V? Go to step 11.Go to step 12.
11 CHECK OUTPUT SIGNAL EMITTED FROM
TCM.
Measure the signal voltage for TCM while
removing the fuse from FWD switch connector.
Connector & terminal
(B56) No. 14 (+) — Chassis ground (
−):Is the voltage more than 10.5
V?Go to step 12.Replace the TCM.
Transmission Con-
trol Module
(TCM).>
12 CHECK POOR CONTACT.Is there poor contact in FWD
switch circuit?Repair the poor
contact.Replace the TCM.
Transmission Con-
trol Module
(TCM).> Step Check Yes No

4AT(H4DOTC)-116
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure without Diagnostic Trouble Code (DTC)
B: CHECK POWER SWITCH
DIAGNOSIS:
 The LED does not come on when POWER switch is ON.
 The POWER switch circuit is open or shorted.
TROUBLE SYMPTOM:
No POWER mode occurs.
WIRING DIAGRAM:
 LHD model
AT-01856
SBF-4 SBF-1
No.13
i10 B:
B54
TCM A:B56
R92 C: C:
i11
C2
B9
C25
A8
E
E
B54
B56
123456
78910 1112
13
14
15 16 17
1819
2021
2223
24
2526
2728
2930
i10
12345678910
i11
5
4 POWER
POWEROFF HOLD
B37
B98
R92
12
34
56
i2
B375B98
R221
i3
B386
B38
219
32
1234 5610 11 12 13 14 15716
23 3019 20
22 26 27 28 29817
24 3118
25
12 345678910111213141516171819202129303122232425262728
POWER AND HOLD
SWITCH BATTERY IGNITION
SWITCH
COMBINATION
METER
123
89
10411 12
13 14 15 1656
7
1734 12 8910 11
12 13 14 15 16 17 18 19 20 21 22 23 24567
A:
C:
B:
C: