2004 SUBARU FORESTER check engine light

4AT(H4DOTC)-87
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
2 CHECK HARNESS CONNECTOR BETWEEN
TCM AND N–R LOCK SOLENOID.
Measure the resistance of harness between
TCM and chassis ground.
Connector & terminal
(B56) No. 18 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 3.Repair the short
circuit in harness
between TCM and
N–R lock solenoid
connector.
3 CHECK HARNESS CONNECTOR BETWEEN
N–R LOCK SOLENOID AND CHASSIS
GROUND.
Measure the resistance of harness between
N–R lock solenoid and chassis ground.
Connector & terminal
(B117) No. 5 — Chassis ground:Is the resistance less than 1
Ω?Go to step 4.Repair the open
circuit in harness
between chassis
ground terminal
and N–R lock sole-
noid connector.
4 CHECK N–R LOCK SOLENOID.
Measure the resistance between N–R lock
solenoid.
Connector & terminal
(B117) No. 5 — No. 4:Is the resistance 20 — 40 Ω? Go to step 5.Replace the N–R
lock solenoid.
5 CHECK TCM OUTPUT SIGNAL.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Shift the select lever to “D” range.
4) Measure the voltage between TCM and
chassis ground.
Connector & terminal
(B56) No. 18 (+) — Chassis ground (
−):Is the voltage more than 10.5
V?Go to step 6.Go to step 7.
6 CHECK OUTPUT SIGNAL FROM TCM.
1) Lift-up the vehicle and place rigid racks.
N
OTE:
Raise all wheels off ground.
2) Start the engine.
3) Shift the select lever “D” range and slowly
increase vehicle speed to 20 km/h (12 MPH).
NOTE:
The speed difference between front and rear
wheels may light ABS warning light, but this indi-
cates no malfunction. When AT control diagnosis
is finished, perform the ABS memory clearance
procedure of on-board diagnostics system.
4) Measure the voltage between TCM and
chassis ground.
Connector & terminal
(B56) No. 18 (+) — 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
cause. Repair the
harness or connec-
tor in reverse inhibi-
tor control circuit.Go to step 7.
7 CHECK POOR CONTACT.Is there poor contact in the
reverse inhibitor control circuit?Repair the poor
contact.Replace the TCM.
Transmission Con-
trol Module
(TCM).> Step Check Yes No

4AT(H4DOTC)-90
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
8 CHECK INPUT SIGNAL FOR TCM.
1) Connect the connectors to TCM and trans-
mission.
2) Lift-up the vehicle and place rigid racks.
N
OTE:
Raise all wheels off ground.
3) Start the engine and set vehicle in 20 km/h
(12 MPH) condition.
N
OTE:
The speed difference between front and rear
wheels may light the ABS warning light, but this
indicates no malfunction. When AT control diag-
nosis is finished, perform the ABS memory
clearance procedure of on-board diagnostics
system. Mode.>
4) Measure the AC voltage between TCM
connector terminals.
Connector & terminal
(B55) No. 24 (+) — No. 23 (
−):Is the voltage more than AC 2
V?Go to step 10.Replace the rear
vehicle speed sen-
sor.
9 CHECK INPUT SIGNAL FOR TCM USING
OSCILLOSCOPE.
1) Connect the connectors to TCM and trans-
mission.
2) Lift-up the vehicle and place rigid racks.
NOTE:
Raise all wheels off ground.
3) Set the oscilloscope to TCM connector ter-
minals.
Connector & terminal
Positive probe; (B55) No. 24:
Earth lead; (B55) No. 23:
4) Start the engine and set vehicle in 20 km/h
(12 MPH) condition.
NOTE:
The speed difference between front and rear
wheels may light the ABS warning light, but this
indicates no malfunction. When AT control diag-
nosis is finished, perform the ABS memory
clearance procedure of on-board diagnostics
system. Mode.>
5) Measure the signal voltage indicated on
oscilloscope.Is the voltage more than AC 2
V?Go to step 10.Replace the rear
vehicle speed sen-
sor.
10 CHECK POOR CONTACT.Is there poor contact in rear
vehicle speed sensor circuit?Repair the poor
contact.Replace the TCM.
Transmission Con-
trol Module
(TCM).> Step Check Yes No

4AT(H4DOTC)-92
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
5 CHECK OUTPUT SIGNAL FROM TCM.
1) Connect the connectors to TCM and trans-
mission.
2) Turn the ignition switch to ON (engine OFF).
3) Shift the select lever to “P” range.
4) Throttle is fully closed.
5) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B56) No. 4 (+) — Chassis ground (
−):Is the voltage less than 1 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 with throttle fully
open.
Connector & terminal
(B56) No. 4 (+) — Chassis ground (
−):Is the voltage more than 10.5
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 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) Turn the ignition switch to ON (engine OFF)
and turn Subaru Select Monitor switch to ON.
4) Move the select lever to “N” range with
throttle fully close (vehicle speed 0 km/h (0
MPH)).
5) Read data of transfer duty solenoid using
Subaru Select Monitor.
 Transfer duty solenoid is indicated in “%”.Is the value 5%? Go to step 8.Go to step 9.
8 CHECK OUTPUT SIGNAL EMITTED FROM
TCM USING SUBARU SELECT MONITOR.
1) Shift the select lever to “D” range with throt-
tle fully open (vehicle speed 0 km/h (0 MPH)).
2) Read the data of transfer duty solenoid
using Subaru Select Monitor.
 Transfer duty solenoid is indicated in “%”.Is the value 90 — 95%? 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 9.
9 CHECK POOR CONTACT.Is there poor contact in transfer
duty solenoid circuit?Repair the poor
contact.Replace the TCM.
Transmission Con-
trol Module
(TCM).> Step Check Yes No

4AT(H4DOTC)-98
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
10 CHECK INPUT SIGNAL FOR TCM.
1) Connect the connectors to TCM, throttle
position sensor and ECM.
2) Turn the ignition switch to ON (engine
OFF).
3) Close the throttle completely.
4) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B55) No. 19 (+) — Chassis ground (
−):Is the voltage more than 0.2 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 throttle posi-
tion sensor circuit.Go to step 20.
11 CHECK INPUT SIGNAL FOR TCM USING
SUBARU SELECT MONITOR.
1) Connect the connectors to TCM, throttle
position sensor and ECM.
2) Connect the Subaru Select Monitor to data
link connector.
3) Turn the ignition switch to ON (engine OFF).
4) Turn the Subaru Select Monitor switch to ON.
5) Close the throttle completely.
6) Read the data of throttle position sensor
using Subaru Select Monitor.
 Throttle position sensor input signal is indi-
cated.Is the voltage more than 0.2 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 throttle posi-
tion sensor circuit.Go to step 20.
12 CHECK ACCELERATOR PEDAL POSITION
SENSOR.
1) Disconnect the connector from accelerator
pedal position sensor.
2) Measure the resistance between accelera-
tor pedal position sensor connector recepta-
cle’s terminals.
Connector & terminal
No. 1 — No. 2:Is the resistance 0.75 — 3.15
kΩ?Go to step 13.Replace the accel-
erator pedal posi-
tion sensor.
13 CHECK ACCELERATOR PEDAL POSITION
SENSOR.
Measure the resistance between accelerator
pedal position sensor connector receptacle’s
terminals.
Connector & terminal
No. 3 — No. 2:Is the resistance 0.15 — 0.63
kΩ?Go to step 14.Replace the accel-
erator pedal posi-
tion sensor.
14 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ACCELERATOR PEDAL POSI-
TION SENSOR.
1) Disconnect the connector from TCM.
2) Measure the resistance of harness
between TCM and accelerator pedal position
sensor connector.
Connector & terminal
(B55) No. 19 — (E13) No. 3:Is the resistance less than 1
Ω?Go to step 15.Repair the open cir-
cuit in harness
between TCM and
accelerator pedal
position sensor
connector, and
poor contact in cou-
pling connector.
15 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ACCELERATOR PEDAL POSI-
TION SENSOR.
Measure the resistance of harness between
TCM connector and chassis ground.
Connector & terminal
(B55) No. 19 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 16.Repair the short cir-
cuit in harness
between TCM and
accelerator pedal
position sensor
connector. Step Check Yes No

4AT(H4DOTC)-99
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
16 CHECK HARNESS CONNECTOR BETWEEN
ECM AND ACCELERATOR PEDAL POSI-
TION SENSOR.
1) Disconnect the connector from ECM.
2) Measure the resistance of harness
between accelerator pedal position sensor
connector and chassis ground.
Connector & terminal
(E13) No. 2 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 17.Repair the short
circuit in harness
between ECM and
accelerator pedal
position sensor.
17 PREPARE SUBARU SELECT MONITOR.Do you have a Subaru Select
Monitor?Go to step 19.Go to step 18.
18 CHECK INPUT SIGNAL FOR TCM.
1) Connect the connectors to TCM, accelera-
tor pedal position sensor and ECM.
2) Turn the ignition switch to ON (engine OFF).
3) Close the throttle completely.
4) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B55) No. 19 (+) — Chassis ground (
−):Is the voltage more than 0.4 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 accelerator
pedal position sen-
sor circuit.Go to step 20.
19 CHECK INPUT SIGNAL FOR TCM USING
SUBARU SELECT MONITOR.
1) Connect the connectors to TCM, accelera-
tor pedal position sensor and ECM.
2) Connect the Subaru Select Monitor to data
link connector.
3) Turn the ignition switch to ON (engine OFF).
4) Turn the Subaru Select Monitor switch to ON.
5) Close the throttle completely.
6) Read the data of accelerator pedal position
sensor using Subaru Select Monitor.
 Accelerator pedal position sensor input sig-
nal is indicated.Is the voltage more than 0.4 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 accelerator
pedal position sen-
sor circuit.Go to step 20.
20 CHECK POOR CONTACT.Is there poor contact in sensor
circuit?Repair the poor
contact.Replace the TCM.
Transmission Con-
trol Module
(TCM).> Step Check Yes No

4AT(H4DOTC)-103
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
2 CHECK GROUND CIRCUIT OF ECM.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM and engine ground.
Connector & terminal
(B134) No. 7 — Engine ground:
(B134) No. 6 — Engine ground:
(B135) No. 1 — Engine ground:
(B135) No. 4 — Engine ground:
(B135) No. 12 — Engine ground:
(B136) No. 19 — Engine ground:
(B137) No. 1 — Engine ground:
(B137) No. 2 — Engine ground:
(B137) No. 7 — Chassis ground:Is the resistance less than 5
Ω?Go to step 3.Repair the open cir-
cuit in harness
between ECM con-
nector and engine
ground terminal.
3 CONFIRM MODEL.Is the vehicle 2.0 L model? Go to step 4.Go to step 11.
4 CHECK THROTTLE POSITION SENSOR.
1) Disconnect the connector from throttle
position sensor.
2) Measure the resistance between throttle
position sensor connector receptacle’s termi-
nals.
Connector & terminal
No. 1 — No. 2:Is the resistance 2.5 — 6 kΩ? Go to step 5.Replace the throt-
tle position sensor.
5 CHECK THROTTLE POSITION SENSOR.
Measure the resistance between throttle posi-
tion sensor connector receptacle’s terminals.
Connector & terminal
No. 2 — No. 3:Is the resistance 0.5 — 4.5
kΩ?Go to step 6.Replace the throt-
tle position sensor.
6 CHECK HARNESS CONNECTOR BETWEEN
TCM AND THROTTLE POSITION SENSOR.
1) Disconnect the connector from TCM.
2) Measure the resistance of harness
between TCM connector and chassis ground.
Connector & terminal
(B55) No. 19 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 7.Repair the short
circuit in harness
between TCM and
throttle position
sensor connector.
7 CHECK HARNESS CONNECTOR BETWEEN
ECM AND THROTTLE POSITION SENSOR.
1) Disconnect the connector from ECM.
2) Measure the resistance of harness
between ECM connector and throttle position
sensor connector.
Connector & terminal
(E13) No. 2 — (B135) No. 19:Is the resistance less than 1
Ω?Go to step 8.Repair the short
circuit in harness
between ECM and
throttle position
sensor.
8 PREPARE SUBARU SELECT MONITOR.Do you have a Subaru Select
Monitor?Go to step 10.Go to step 9.
9 CHECK INPUT SIGNAL FOR TCM.
1) Connect the connectors to TCM, throttle
position sensor and ECM.
2) Turn the ignition switch to ON (engine OFF).
3) Open the throttle fully.
4) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B55) No. 19 (+) — Chassis ground (
−):Is the voltage more than 4.6 V? Go to step 18.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 circuit. Step Check Yes No

4AT(H4DOTC)-104
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
10 CHECK INPUT SIGNAL FOR TCM USING
SUBARU SELECT MONITOR.
1) Connect the connectors to TCM, throttle
position sensor and ECM.
2) Connect the Subaru Select Monitor to data
link connector.
3) Turn the ignition switch to ON (engine OFF).
4) Turn the Subaru Select Monitor switch to ON.
5) Open the throttle fully.
6) Read the data of throttle position sensor
using Subaru Select Monitor.
 Throttle position sensor input signal is indi-
cated.Is the voltage more than 4.6 V? Go to step 18.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 circuit.
11 CHECK ACCELERATOR PEDAL POSITION
SENSOR.
1) Disconnect the connector from accelerator
pedal position sensor.
2) Measure the resistance between accelera-
tor pedal position sensor connector recepta-
cle’s terminals.
Connector & terminal
No. 1 — No. 2:Is the resistance 0.75 — 3.15
kΩ?Go to step 12.Replace the accel-
erator pedal posi-
tion sensor.
12 CHECK ACCELERATOR PEDAL POSITION
SENSOR.
Measure the resistance between accelerator
pedal position sensor connector receptacle’s
terminals.
Connector & terminal
No. 2 — No. 3:Is the resistance 0.15 — 0.63
kΩ?Go to step 13.Replace the accel-
erator pedal posi-
tion sensor.
13 CHECK HARNESS CONNECTOR BETWEEN
TCM AND ACCELERATOR PEDAL POSI-
TION SENSOR.
1) Disconnect the connector from TCM.
2) Measure the resistance of harness
between TCM connector and chassis ground.
Connector & terminal
(B55) No. 19 — Chassis ground:Is the resistance more than 1
MΩ?Go to step 14.Repair the short
circuit in harness
between TCM and
accelerator pedal
position sensor
connector.
14 CHECK HARNESS CONNECTOR BETWEEN
ECM AND ACCELERATOR PEDAL POSI-
TION SENSOR.
1) Disconnect the connector from ECM.
2) Measure the resistance of harness
between ECM connector and accelerator pedal
position sensor connector.
Connector & terminal
(E13) No. 2 — (B135) No. 19:Is the resistance less than 1
Ω?Go to step 15.Repair the short
circuit in harness
between ECM and
accelerator pedal
position sensor.
15 PREPARE SUBARU SELECT MONITOR.Do you have a Subaru Select
Monitor?Go to step 17.Go to step 16. Step Check Yes No

4AT(H4DOTC)-105
AUTOMATIC TRANSMISSION (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
16 CHECK INPUT SIGNAL FOR TCM.
1) Connect the connectors to TCM, accelera-
tor pedal position sensor and ECM.
2) Turn the ignition switch to ON (engine OFF).
3) Open the throttle fully.
4) Measure the voltage between TCM con-
nector and chassis ground.
Connector & terminal
(B55) No. 19 (+) — Chassis ground (
−):Is the voltage more than 4.6 V? Go to step 18.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 accelerator
pedal position sen-
sor circuit.
17 CHECK INPUT SIGNAL FOR TCM USING
SUBARU SELECT MONITOR.
1) Connect the connectors to TCM, accelera-
tor pedal position sensor and ECM.
2) Connect the Subaru Select Monitor to data
link connector.
3) Turn the ignition switch to ON (engine OFF).
4) Turn the Subaru Select Monitor switch to ON.
5) Open the throttle fully.
6) Read the data of accelerator pedal position
sensor using Subaru Select Monitor.
 Accelerator pedal position sensor input sig-
nal is indicated.Is the voltage more than 4.6 V? Go to step 18.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 accelerator
pedal position sen-
sor circuit.
18 CHECK POOR CONTACT.Is there poor contact in sensor
circuit?Repair the poor
contact.Replace the TCM.
Transmission Con-
trol Module
(TCM).> Step Check Yes No