2004 SUBARU FORESTER check engine

AC-10
HVAC SYSTEM (AUTO A/C)(DIAGNOSTIC)
Diagnostic Chart for Self-Diagnosis
Step Check Yes No
1 SELECT CONTROL PANEL TO SELF-DIAG-
NOSIS MODE.
1) Turn the ignition switch to OFF.
2) Start the engine while pressing defroster
switch and A/C switch.
N
OTE:
Self-diagnosis can also be performed with the
ignition switch ON, but start the engine be-
cause telling the magnet clutch operation is dif-
ficult.
3) The LED in A/C control panel blinks.Does the self-diagnosis mode
operate?Go to step 2. C OR SELF-DIAG-
NOSIS SYS-
TEMS DO NOT
OPERATE, Diag-
nostics for A/C
System Malfunc-
tion.>
2 CHECK LED ILLUMINATION.
Make sure that three LED blink in turn on A/C
control panel (5 patterns are repeated 2 times).Do all LED blink? Go to step 3.Go to step 5.
3 CHECK SENSORS MALFUNCTION.
1) After completing the LED check or when
AUTO switch is pressed, the A/C switch LED
illuminates, and then the sensor check is
started.
2) Check the input signal of each sensor in
turn. If there are any trouble for each sensor,
DEF, MODE and fan speed LEDs are blinked.
Also check for each sensor is possible respec-
tively every time AUTO switch is pressed. (At
this time, the AUTO switch LED illuminates.)
3) If there is no trouble, DEF, MODE and fan
speed LEDs are turned off.
N
OTE:
Rear window defogger LED illuminates in case
of stored malfunction but does not illuminate in
case of present malfunction.Does each DEF, MODE and
fan speed LED turn off?Go to step 4.Confirm the com-
bination of illumi-
nating LEDs by
using Sensor
Check Table, and
identify the mal-
functioning sensor
before repairing.
SENSOR CHECK
TABLE, OPERA-
TION, Diagnostic
Chart for Self-
Diagnosis.>
4 CHECK OPERATION OF EACH ACTUATOR,
COMPRESSOR AND FAN MOTOR.
1) Press the FRESH/RECIRC switch
(FRESH/RECIRC switch LED illuminates at
this time.).
2) Refer to OPERATING MODE TABLE to
check the operation of each actuator, compres-
sor and fan motor. ING MODE TABLE, OPERATION, Diagnostic
Chart for Self-Diagnosis.>
Also check for each step is possible respec-
tively every time AUTO switch pressed. (At this
time, the AUTO switch LED illuminates.)Does each actuator, compres-
sor and fan motor operate
according to operating mode
table?Press the OFF
switch or turn the
ignition switch to
OFF and finish the
self-diagnosis
mode.Refer to each
diagnostics chart
for actuator, com-
pressor and fan
motor, and repair
the malfunctioning
par t as necessary.
Diagnostics for A/
C System Mal-
function.> AC-21, Diagnostic
Procedure for
Actuators.>
5 CHECK POOR CONTACT.
Check the auto A/C control module connector
for poor contact.Is there a poor contact in con-
nector?Replace the auto
A/C control mod-
ule.Repair the con-
nector.

AC-18
HVAC SYSTEM (AUTO A/C)(DIAGNOSTIC)
Diagnostics for A/C System Malfunction
Step Check Yes No
1 CHECK FUSE.
1) Turn the ignition switch to OFF.
2) Remove the main fan fuse and sub fan fuse
in main fuse box.
3) Check the condition of fuse.Is the fuse blown out? Replace the fuse. Go to step 2.
2 CHECK THE POWER SUPPLY TO PRES-
SURE SWITCH.
1) Disconnect the connector from pressure
switch.
2) Turn the ignition switch to ON.
3) Measure the voltage between harness con-
nector and chassis ground.
Connector & terminal
(F79) No. 1 (+) — Chassis ground (
−):Is the voltage more than 10 V? Go to step 3.Repair the har-
ness for pressure
switch power sup-
ply circuit.
3 CHECK THE HARNESS BETWEEN PRES-
SURE SWITCH AND A/C RELAY HARNESS.
1) Turn the ignition switch to OFF.
2) Remove the A/C relay in the main fuse box.
3) Measure the resistance between A/C relay
and pressure switch connector.
Connector & terminal
(F27) No. 17 — (F79) No. 2:Is the resistance less than 1
Ω?Go to step 4.Repair the har-
ness between A/C
relay and pres-
sure switch.
4 CHECK THE PRESSURE SWITCH.
Measure the resistance between pressure
switch terminals.
Te r m i n a l s
No. 1 — No. 2:Is the resistance less than 1
Ω?Go to step 5.Replace the pres-
sure switch.
5 CHECK THE A/C CUT SIGNAL CIRCUIT.
1) Disconnect the connector from auto A/C
control module.
2) Measure the resistance between auto A/C
control module and pressure switch connector.
Connector & terminal
(i48) No. 10 — (F79) No. 2:Is the resistance less than 1
Ω?Go to step 6.Repair the har-
ness between auto
A/C control mod-
ule and pressure
switch.
6 CHECK THE A/C ON SIGNAL CIRCUIT.
1) Disconnect the connector from ECM.
2) Measure the resistance between ECM and
auto A/C control module connector.
Connector & terminal
Turbo model
(B137) No. 17 — (i49) No. 17:
Non-turbo model
(B136) No. 11 — (i49) No. 17:Is the resistance less than 1
Ω?Go to step 7.Repair the har-
ness between auto
A/C control mod-
ule and ECM.
7 CHECK A/C RELAY.
1) Remove the A/C relay in main fuse box.
2) Check the A/C relay. INSPECTION, Relay and Fuse.>Is the operation of the relay
OK?Go to step 8.Replace the A/C
relay.
8 CHECK POWER SUPPLY TO MAGNET
CLUTCH OF A/C COMPRESSOR.
1) Turn the ignition switch to OFF, and then
connect the A/C relay connector and all
removed connectors.
2) Start the engine, and turn A/C switch to
ON.
3) Set the temperature control dial to maxi-
mum cold position.
4) Measure the voltage between magnet
clutch harness connector and chassis ground.
Connector & terminal
(F24) No. 1 (+) — Chassis ground (
−):Is the voltage more than 10.5 V
(at normal temperature)?Go to step 9.Repair the har-
ness for power
supply line of A/C
compressor.

AC-19
HVAC SYSTEM (AUTO A/C)(DIAGNOSTIC)
Diagnostics for A/C System Malfunction
9 CHECK OPERATION OF MAIN FAN MOTOR.
1) Start the engine and turn the A/C switch to
ON.
2) Check the operation of main fan motor.Does the main fan motor oper-
ate normally?Go to step 14.Go to step 10.
10 CHECK POWER SUPPLY TO MAIN FAN MO-
TOR.
CAUTION:
Be careful not to overheat the engine during
repair.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from main fan
motor.
3) Start the engine, and warm it up until
engine coolant temperature increases over
100°C (212°F).
4) Stop the engine and turn ignition switch to
ON.
5) Measure the voltage between main fan
motor harness connector and chassis ground.
Connector & terminal
Except turbo AT model:
(F17) No. 2 (+) — Chassis ground (
−):
Turbo AT model:
(F17) No. 1 (+) — Chassis ground (
−):Is the voltage more than 10 V? Go to step 11.Repair the har-
ness for main fan
motor power sup-
ply circuit.
11 CHECK GROUND CIRCUIT OF MAIN FAN
MOTOR.
Measure the resistance between main fan
motor harness connector and chassis ground.
Connector & terminal
Except turbo AT model:
(F17) No. 1 — Chassis ground:
Turbo AT model:
(F17) No. 2 — Chassis ground:Is the resistance less than 1
Ω?Go to step 12.Repair the har-
ness for main fan
motor ground cir-
cuit.
12 CHECK MAIN FAN MOTOR.
Connect the battery positive (+) terminal to ter-
minal No. 2, and ground (−) terminal to termi-
nal No. 1 of main fan motor connector to make
sure that main fan motor rotate.Does the main fan rotate? Go to step 13.Replace the main
fan motor.
13 CHECK POOR CONTACT IN MAIN FAN MO-
TOR CONNECTOR.
Check poor contact in main fan motor harness
connector.Is there poor contact in con-
nector?Go to step 14.Repair the poor
contact in main fan
motor connector.
14 CHECK OPERATION OF SUB FAN MOTOR.
1) Start the engine and turn the A/C switch to
ON.
2) Check the operation of sub fan motor.Does the sub fan motor oper-
ate normally?Go to step 19.Go to step 15. Step Check Yes No

AC-20
HVAC SYSTEM (AUTO A/C)(DIAGNOSTIC)
Diagnostics for A/C System Malfunction
15 CHECK POWER SUPPLY TO SUB FAN MO-
TOR.
CAUTION:
Be careful not to overheat the engine during
repair.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from sub fan
motor.
3) Start the engine, and warm it up until
engine coolant temperature increases over
100°C (212°F).
4) Stop the engine and turn ignition switch to
ON.
5) Measure the voltage between sub fan
motor harness connector and chassis ground.
Connector & terminal
Except turbo AT model:
(F16) No. 2 (+) — Chassis ground (
−):
Turbo AT model:
(F16) No. 1 (+) — Chassis ground (
−):Is the voltage more than 10 V? Go to step 16.Repair the har-
ness for sub fan
motor power sup-
ply circuit.
16 CHECK GROUND CIRCUIT OF SUB FAN
MOTOR.
Measure the resistance between sub fan motor
harness connector and chassis ground.
Connector & terminal
Except turbo AT model:
(F16) No. 1 — Chassis ground:
Turbo AT model:
(F16) No. 2 — Chassis ground:Is the resistance less than 1
Ω?Go to step 17.Repair the har-
ness for sub fan
motor ground cir-
cuit.
17 CHECK SUB FAN MOTOR.
Connect the battery positive (+) terminal to ter-
minal No. 2, and ground (−) terminal to termi-
nal No. 1 of sub fan motor connector to make
sure that sub fan motor rotate.Does the sub fan motor rotate? Go to step 18.Replace the sub
fan motor.
18 CHECK POOR CONTACT IN SUB FAN MO-
TOR CONNECTOR.
Check poor contact in sub fan motor connec-
tor.Is there poor contact in con-
nector?Go to step 19.Repair the poor
contact in sub fan
motor connector.
19 CHECK POOR CONTACT IN AUTO A/C
CONTROL MODULE CONNECTOR.
Check poor contact in auto A/C control module
connector.Is there poor contact in con-
nector?Replace the auto
A/C control mod-
ule.Repair the con-
nector. Step Check Yes No

AB-8
AIRBAG SYSTEM (DIAGNOSTIC)
General Description
B: INSPECTION
Before diagnosing, check the following items that might be related to the engine problem:
1. BATTERY
Measure the battery voltage and specific gravity of electrolyte.
Standard voltage: 12 V
Specific gravity: Above 1.260
C: PREPARATION TOOL
1. SPECIAL TOOL
 TEST HARNESS M
ILLUSTRATION TOOL NUMBER DESCRIPTION REMARKS
98299FE020 TEST HARNESS M  Used when measuring voltage, resistance of
airbag system.
 Used with test harness T (98299SA060).
5M3M 4M
1M
2M
ST98299FE020
AB-00425
5M
1
21
Lg
2
8
18
5
16
7
6
9
1
11
10
4
2
Lg
YL
Y
100
GW
3M 4M
1M
2M
12
65 21
4334 12
56 21 1
234 5678
91011
12 13 14 15 16 17 18
1
2
3
4
5
6
2M 1M 4M 3M
5M6
5
4
3
2
1

AB-51
AIRBAG SYSTEM (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK DRIVERS AIRBAG MODULE.
1) Turn the ignition switch to OFF, disconnect
the battery ground cable, and wait more than
20 seconds.
2) Remove the driver’s airbag module. to AB-14, Driver’s Airbag Module.>
3) Connect the connector (AB2) to connector
(1N) in test harness N.
4) Connect the airbag resistor to connector
(2N) in test harness N.
5) Connect the battery ground cable and turn
the ignition switch to ON.Is the airbag warning light
turned on normally?Replace the
driver’s airbag
module. AB-14, Driver’s
Airbag Module.>Go to step 2.
2 CHECK ROLL CONNECTOR.
1) Turn the ignition switch to OFF, disconnect
the battery ground cable, and wait more than
20 seconds.
2) Disconnect the test harness N from the
connector (AB2).
3) Remove the instrument panel lower cover
and disconnect the connector (AB21) from
(AB26).
4) Connect the connector (1F) in test harness
F to connector (AB21).
5) Connect the airbag resistor to connector
(3F) in test harness F.
6) Connect the battery ground cable and turn
the ignition switch to ON.Is the airbag warning light
turned on normally?Replace the roll
connector. AB-20, Roll Con-
nector.>Go to step 3.
3 CHECK AIRBAG MAIN HARNESS.
1) Turn the ignition switch to OFF, disconnect
the battery ground cable, and wait more than
20 seconds.
2) Disconnect the airbag resistor from the
connector (3F) in test harness F.
3) Remove the glove box, and disconnect the
connectors (AB4) and passenger’s airbag
module (AB27).
4) Disconnect the connector (AB3) from the
airbag control module, and connect the con-
nector (1R) in test harness R. Airbag Control Module.>
5) Connect the battery ground cable and turn
the ignition switch to ON. (engine OFF)
6) Measure the voltage between connector
(2R) in test harness R and the chassis ground.
Connector & terminal
(2R) No. 2 (+) — Chassis ground (
−):
(2R) No. 4 (+) — Chassis ground (
−): Is the voltage less than 1 V? Replace the airbag
control module.
Airbag Control
Module.>Replace the airbag
main harness with
body harness.

SB-9
SEAT BELT SYSTEM
Seat Belt Warning System
14 CHECK HARNESS BETWEEN TCU AND
SEAT BELT TIMER MODULE.
Measure the resistance between seat belt
timer module harness connector and chassis
ground.
Connector & terminal
(B44) No. 7 — Chassis ground:Is the resistance less than 10
Ω?Go to step 15.Repair the short of
harness.
15 CHECK SEAT BELT TIMER MODULE OUT-
PUT SIGNAL.
1) Turn the ignition switch to ON.
2) Measure the voltage between seat belt
timer module harness connector and chassis
ground.
Connector & terminal
(B44) No. 2 (+) — Chassis ground (–):Is the voltage more than 10 V? Go to step 16.Check the wiring
harness and com-
bination meter,
and then repair or
replace them.
16 CHECK POOR CONTACT.
Check the poor contact of seat belt warning
light circuit.Is there any poor contact
occurs?Repair the poor
contact.Go to step 17.
17 CHECK SEAT BELT TIMER MODULE.
1) Connect all connectors.
2) Lift-up the vehicle and place rigid racks.
NOTE:
Raise all wheels off floor.
3) Hold the tang plate disconnected from seat
belt buckle.
4) Start the engine, and set the vehicle speed
less than 19 km/h (12 MPH)
N
OTE:
The speed difference between front and rear
wheels may light the ABS warning light, but this
indicates no malfunction. When diagnosis is fin-
ished, perform the ABS memory clearance pro-
cedure of OBD system. Memory Mode.>
Check seat belt warning light comes on.Does the seat belt warning
light come on?Go to step 18.Replace the seat
belt timer module.
18 CHECK SEAT BELT TIMER MODULE.
1) Connect all connectors.
2) Lift-up the vehicle and place rigid racks.
N
OTE:
Raise all wheels off floor.
3) Hold the tang plate disconnected from seat
belt buckle.
4) Start the engine, and set the vehicle speed
more than 25 km/h (16 MPH).
NOTE:
The speed difference between front and rear
wheels may light the ABS warning light, but this
indicates no malfunction. When diagnosis is fin-
ished, perform the ABS memory clearance pro-
cedure of OBD system. Memory Mode.>
Check seat belt warning light comes on and
buzzer beeps.Does the seat belt warning
light come on and buzzer
beep?Temporary poor
contact of connec-
tor or harness may
be the cause.
Check the poor
contact.Replace the seat
belt timer module. Step Check Yes No

ET-3
ENTERTAINMENT
Radio System
2. Radio System
A: WIRING DIAGRAM
1. RADIO

B: INSPECTION
Symptom Repair order
No power coming in. (No display and no sound from speakers.) (1) Check the fuse and power supply for radio.
(2) Check the radio ground.
(3) Remove the radio for repair.
A specific speaker does not operate. (1) Check the speaker.
(2) Check the output circuit between radio and speaker.
Radio generates noise with engine running. (1) Check the radio ground.
(2) Check the generator.
(3) Check the ignition coil.
(4) Remove the radio for repair.
AM and FM modes are weak or noisy. (1) Check the antenna.
(2) Check the antenna amplifier.
(3) Check the noise suppressor.
(4) Check the radio ground.
(5) Remove the radio for repair.