2004 SUBARU FORESTER automatic transmission

4AT(H4DOTC)-69
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
P: DTC P0748 PRESSURE CONTROL SOLENOID “A” ELECTRICAL
DTC DETECTING CONDITION:
Output signal circuit of line pressure linear solenoid is open or shorted.
TROUBLE SYMPTOM:
Excessive shift shock.
WIRING DIAGRAM:
Step Check Yes No
1 CHECK HARNESS CONNECTOR BETWEEN
TCM AND TRANSMISSION.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from transmis-
sion and TCM.
3) Measure the resistance of harness
between TCM and transmission connector.
Connector & terminal
(B56) No. 19 — (B11) No. 2:
(B56) No. 20 — (B11) No. 1:Is the resistance less than 1
Ω?Go to step 2.Repair the open
circuit in harness
between TCM and
transmission con-
nector.
2 CHECK HARNESS CONNECTOR BETWEEN
TCM AND CHASSIS GROUND.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B56) No. 19 — Chassis ground:
(B56) No. 20 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 3.Repair the short
circuit in harness
between TCM and
transmission con-
nector.
3 CHECK LINE PRESSURE LINEAR SOLE-
NOID.
Measure the resistance between transmission
connector receptacle’s terminals.
Connector & terminal
(T4) No. 1 — No. 2:Is the resistance 4 — 6 Ω? Go to step 4.Go to step 10.
AT-01847
19
B56
B11
AT11
T4 TCM
B11
1
234
56
78
9
1314
15
20
19 1716 10 1112
18
422021
B56AT11
12 78 956 34
10 11 12 19 20 21
29 30 31 13 14 15 16 17
27 2818
22 23 24 25 263412
TRANSMISSIONLINE
PRESSURE
LINEAR
SOLENOID

4AT(H4DOTC)-70
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
4 PREPARE SUBARU SELECT MONITOR.Do you have a Subaru Select
Monitor?Go to step 7.Go to step 5.
5 CHECK OUTPUT SIGNAL FROM TCM.
1) Connect all connectors.
2) Start the engine and warm-up the engine
until ATF temperature is above 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) Turn the ignition switch to ON (engine
OFF).
4) Shift the select lever to “R” range.
5) Close the throttle fully.
6) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B56) No. 20 (+) — Chassis ground (
−):Is the voltage 5.0 — 7.0 V? Go to step 6.Go to step 9.
6 CHECK OUTPUT SIGNAL FROM TCM.
1) Open the throttle fully.
2) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B56) No. 20 (+) — Chassis ground (
−):Is the voltage 3.0 — 5.0 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 transmission.Go to step 9.
7 CHECK OUTPUT SIGNAL FROM TCM US-
ING SUBARU SELECT MONITOR.
1) Connect the connectors to TCM and trans-
mission.
2) Connect the Subaru Select Monitor to data
link connector.
3) Start the engine and turn Subaru Select
Monitor switch to ON.
4) Warm-up the transmission until ATF tem-
perature is above 80°C (176°F).
NOTE:
If ambient temperature is below 0°C (32°F),
drive the vehicle until ATF reaches its operating
temperature.
5) Stop the engine and turn ignition switch to
ON (engine OFF).
6) Shift the select lever to “R” range.
7) Read the data of line pressure linear sole-
noid using Subaru Select Monitor.
 Line pressure linear solenoid is indicated in
“%”.
8) Throttle is fully closed.Is the value 45 — 50%? Go to step 8.Go to step 9. Step Check Yes No

4AT(H4DOTC)-71
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
8 CHECK OUTPUT SIGNAL FROM TCM US-
ING SUBARU SELECT MONITOR.
1) Fully open the throttle.
2) Shift the select lever to “R” range. (engine
OFF)
3) Read the data of line pressure linear sole-
noid.Is the value 20 — 40%? 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 transmission.Go to step 9.
9 CHECK POOR CONTACT.Is there poor contact in line
pressure linear solenoid cir-
cuit?Repair the poor
contact.Replace the TCM.
Transmission Con-
trol Module
(TCM).>
10 CHECK LINE PRESSURE LINEAR SOLE-
NOID (IN TRANSMISSION).
1) Remove the transmission connector from
bracket.
2) Drain the ATF.
CAUTION:
Do not drain the ATF until it cools down.
3) Remove the oil pan, and disconnect con-
nector from line pressure linear solenoid.
4) Measure the resistance between line pres-
sure linear solenoid connector and transmis-
sion ground.
Connector & terminal
(AT11) No. 2 — No. 4:Is the resistance 2.0 — 4.5 Ω? Go to step 11.Replace the con-
trol valve body.
Control Valve
Body.>
11 CHECK HARNESS CONNECTOR BETWEEN
TRANSMISSION AND LINE PRESSURE LIN-
EAR SOLENOID.
Measure the resistance of harness between
line pressure linear solenoid and transmission
connector.
Connector & terminal
(T4) No. 2 — (AT11) No. 4:
(T4) No. 1 — (AT11) No. 2:Is the resistance less than 1
Ω?Go to step 12.Repair the open cir-
cuit in harness
between line pres-
sure linear solenoid
and transmission
connector.
12 CHECK HARNESS CONNECTOR BETWEEN
TRANSMISSION AND LINE PRESSURE LIN-
EAR SOLENOID.
Measure the resistance of harness between
transmission connector and transmission
ground.
Connector & terminal
(T4) No. 1 — Transmission ground:
(T4) No. 2 — Transmission ground:Is the resistance more than 1
MΩ?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 line pressure
linear solenoid and
transmission.Repair the short
circuit in harness
between line pres-
sure linear sole-
noid and
transmission con-
nector. Step Check Yes No

4AT(H4DOTC)-72
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Q: DTC P0753 SHIFT SOLENOID “A” ELECTRICAL
DTC DETECTING CONDITION:
Output signal circuit of low clutch timing solenoid is open or shorted.
TROUBLE SYMPTOM:
Excessive shift shock.
WIRING DIAGRAM:
Step Check Yes No
1 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
(B56) No. 9 — (B11) No. 4:Is the resistance less than 1
Ω?Go to step 2.Repair the open
circuit in harness
between TCM and
transmission con-
nector.
AT-01848
B11
B56
AT12
1
234
56
78
9
1314
15
20
19 1716 10 1112
18
9
B56
B11
AT12
T4 TCM4
2
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
13
4562
LOW CLUTCH
DUTY
SOLENOID
TRANSMISSION

4AT(H4DOTC)-73
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
2 CHECK HARNESS CONNECTOR BETWEEN
TCM AND TRANSMISSION.
Measure the resistance of harness between
TCM connector and transmission ground.
Connector & terminal
(B56) No. 9 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 3.Repair the short
circuit in harness
between TCM and
transmission con-
nector.
3 CHECK LOW CLUTCH DUTY SOLENOID.
Measure the resistance between transmission
connector terminals.
Connector & terminal
(T4) No. 4 — No. 20:Is the resistance 2.0 — 4.5 Ω? Go to step 4.Go to step 10.
4 PREPARE SUBARU SELECT MONITOR.Do you have a Subaru Select
Monitor?Go to step 7.Go to step 5.
5 CHECK OUTPUT SIGNAL FROM TCM.
1) Connect all connectors.
2) Start the engine and warm-up the engine
until ATF temperature is above 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) Turn the ignition switch to ON (engine
OFF).
4) Shift the select lever to “P” or “N” range.
5) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B56) No. 9 (+) — Chassis ground (
−):Is the voltage more than 10.5
V?Go to step 6.Go to step 9.
6 CHECK OUTPUT SIGNAL FROM TCM.
1) Shift the select lever to “D” range.
2) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B56) No. 9 (+) — Chassis ground (
−):Is the voltage less than 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 transmission.Go to step 9. Step Check Yes No

4AT(H4DOTC)-74
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
7 CHECK OUTPUT SIGNAL FROM TCM US-
ING SUBARU SELECT MONITOR.
1) Connect the connectors to TCM and trans-
mission.
2) Connect the Subaru Select Monitor to data
link connector.
3) Start the engine and turn Subaru Select
Monitor switch to ON.
4) Warm-up the transmission until ATF tem-
perature is above 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) Stop the engine and turn ignition switch to
ON (engine OFF).
6) Shift the select lever to “P” or “N” range.
7) Read the data of low clutch duty solenoid
using Subaru Select Monitor.
 Low clutch duty solenoid is indicated in “%”.Is the value 100%? Go to step 8.Go to step 9.
8 CHECK OUTPUT SIGNAL FROM TCM US-
ING SUBARU SELECT MONITOR.
1) Turn the ignition switch to ON (engine
OFF).
2) Shift the select lever to “D” range.
3) Read the data of low clutch duty solenoid.Is the value 0%? 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 transmission.Go to step 9.
9 CHECK POOR CONTACT.Is there poor contact in low
clutch duty solenoid circuit?Repair the poor
contactReplace the TCM.
Transmission Con-
trol Module
(TCM).>
10 CHECK LOW CLUTCH DUTY SOLENOID (IN
TRANSMISSION).
1) Remove the transmission connector from
bracket.
2) Drain the ATF.
CAUTION:
Do not drain the ATF until it cools down.
3) Remove the oil pan, and disconnect con-
nector from low clutch duty solenoid.
4) Measure the resistance between low clutch
duty solenoid connector and transmission
ground.
Connector & terminal
(AT12) No. 2 — Transmission ground:Is the resistance 2.0 — 4.5 Ω? Go to step 11.Replace the con-
trol valve body.
Control Valve
Body.>
11 CHECK HARNESS CONNECTOR BETWEEN
TRANSMISSION AND LOW CLUTCH DUTY
SOLENOID.
Measure the resistance of harness between
low clutch duty solenoid and transmission con-
nector.
Connector & terminal
(T4) No. 4 — (AT12) No. 2:Is the resistance less than 1
Ω?Go to step 12.Repair the open
circuit in harness
between low clutch
duty solenoid and
transmission con-
nector. Step Check Yes No

4AT(H4DOTC)-75
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
12 CHECK HARNESS CONNECTOR BETWEEN
TRANSMISSION AND LOW CLUTCH DUTY
SOLENOID.
Measure the resistance of harness between
transmission connector and transmission
ground.
Connector & terminal
(T4) No. 4 — Transmission ground:Is the resistance more than 1
MΩ?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 low clutch
duty solenoid and
transmission.Repair the short
circuit in harness
between low clutch
duty solenoid and
transmission con-
nector. Step Check Yes No

4AT(H4DOTC)-76
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
R: DTC P0758 SHIFT SOLENOID “B” ELECTRICAL
DTC DETECTING CONDITION:
Output signal circuit of 2-4 brake duty solenoid is open or shorted.
TROUBLE SYMPTOM:
Excessive shift shock.
WIRING DIAGRAM:
Step Check Yes No
1 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 shift transmission connector.
Connector & terminal
(B56) No. 6 — (B11) No. 3:Is the resistance less than 1
Ω?Go to step 2.Repair the open
circuit in harness
between TCM and
transmission con-
nector.
2 CHECK HARNESS CONNECTOR BETWEEN
TCM AND CHASSIS GROUND.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B56) No. 6 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 3.Repair the short
circuit in harness
between TCM and
transmission con-
nector.
3 CHECK 2-4 BRAKE DUTY SOLENOID.
Measure the resistance between transmission
connector terminals.
Connector & terminal
(T4) No. 3 — No. 20:Is the resistance 2.0 — 4.5 Ω? Go to step 4.Go to step 10.
4 PREPARE SUBARU SELECT MONITOR.Do you have a Subaru Select
Monitor?Go to step 7.Go to step 5.
AT-01119
6
B56
B11
AT12
T4 TCM
B11
1
234
56
78
9
1314
15
20
19 1716 10 1112
18
3 6
B56AT12
12 78 956 34
10 11 12 19 20 21
29 30 31 13 14 15 16 17
27 2818
22 23 24 25 2613
4562
TRANSMISSION2-4 BRAKE
DUTY
SOLENOID