check engine light SUBARU FORESTER 2004 Service Repair Manual

EN(H4DOTC 2.5)-6
ENGINE (DIAGNOSTIC)
General Description
13) Diagnostics should be conducted by rotating
with simple, easy operations and proceeding to
complicated, difficult operations. The most impor-
tant thing in diagnostics is to understand the cus-
tomer’s complaint, and distinguish between the
three causes.
14) On the model with ABS, when performing driv-
ing test in jacked-up or lifted-up position, some-
times the warning light may be lit, but this is not a
malfunction of the system. The reason for this is the
speed difference between the front and rear
wheels. After diagnosis of engine control system,
perform the ABS memory clearance procedure of
self-diagnosis function.
B: INSPECTION
Before performing diagnostics, check the following
items which might affect engine problems:
1. BATTERY
1) Measure battery voltage and specific gravity of
electrolyte.
Standard voltage: 12 V
Specific gravity: Above 1.260
2) Check the condition of the main and other fuses,
and harnesses and connectors. Also check for
proper grounding.
2. ENGINE GROUND
Make sure the engine ground terminal is properly
connected to the engine.
C: NOTE
1. GENERAL DESCRIPTION
 On-board diagnosis (OBD) system detects and
indicates a fault in various inputs and outputs of the
complex electronic control. Malfunction indicator
light in the combination meter indicates occurrence
of a fault or trouble.
 Further, against such a failure or sensors as may
disable the drive, the fail-safe function is provided
to ensure the minimal driveability.
 The OBD system incorporated with the vehicles
within this engine family complies with Section
1968.1, California Code of Regulations (OBD-II
regulation). The OBD system monitors the compo-
nents and the system malfunction listed in Engine
Section which affects on emissions.
 When the system decides that a malfunction oc-
curs, malfunction indicator light illuminates. At the
same time of the malfunction indicator light illumi-
nation or blinking, the DTC and a freeze frame en-
gine conditions are stored into on-board computer.
 The OBD system stores freeze frame engine
condition data (engine load, engine coolant tem-
perature, fuel trim, engine speed and vehicle
speed, etc.) into on-board computer when it detects
a malfunction first.
 If the OBD system detects the various malfunc-
tions including the fault of fuel trim or misfire, the
OBD system first stores freeze frame engine condi-
tions about the fuel trim or misfire.
 When the malfunction does not occur again for
three consecutive driving cycles, malfunction indi-
cator light is turned off, but DTC remains at on-
board computer.
 The OBD-II system is capable of communication
with a general scan tool (OBD-II general scan tool)
formed by ISO 9141 CARB.
 The OBD-II diagnostics procedure is different
from the usual diagnosis procedure. When trouble-
shooting the OBD-II models, connect Subaru Se-
lect Monitor or the OBD-II general scan tool to the
vehicle.
EN-01201

EN(H4DOTC 2.5)-25
ENGINE (DIAGNOSTIC)
OBD-II General Scan Tool
2. MODE $01 (CURRENT POWERTRAIN DIAGNOSTIC DATA)
Refers to data denoting the current operating condition of analog input/output, digital input/output and/or the
powertrain system.
A list of the support data and PID (Parameter Identification) codes are shown in the following table.
NOTE:
Refer to OBD-II general scan tool manufacturer’s instruction manual to access generic OBD-II PIDs (MODE
$01).
3. MODE $02 (POWERTRAIN FREEZE FRAME DATA)
Refers to data denoting the operating condition when trouble is sensed by the on-board diagnosis system.
A list of the support data and PID (Parameter Identification) codes are shown in the following table.
NOTE:
Refer to OBD-II general scan tool manufacturer’s instruction manual to access freeze frame data (MODE
$02).
PID Data Unit of measure
01Number of emission-related powertrain DTC, malfunction indicator light status and diagnosis
support information—
03 Fuel system control status—
04 Calculated engine load value%
05 Engine coolant temperature°C
06 Short term fuel trim%
07 Long term whole fuel trim%
0B Intake manifold absolute pressure kPa, mmHg
0C Engine revolutionrpm
0D Vehicle speedkm/h
0E Ignition timing advance°
0F Intake air temperature°C
10 Air flow rate of mass air flow sensor g/sec
11 Throttle valve absolute opening angle %
13 Check whether oxygen sensor is installed. —
15 Oxygen sensor output voltage and short term fuel trim associated with oxygen sensor V and %
1C Available OBD system—
24 A/F value and A/F sensor output voltage — and V
34 A/F value and A/F sensor current — and mA
PID Data Unit of measure
02 DTC that caused CARB required freeze frame data storage —
03 Fuel system control status—
04 Calculated engine load value%
05 Engine coolant temperature°C
06 Short term fuel trim%
07 Long term whole fuel trim%
0B Intake manifold absolute pressure mmHg
0C Engine speedrpm
0D Vehicle speedkm/h
0E Ignition timing advance°
0F Intake air temperature°C
10 Air flow rate of mass air flow sensor g/sec
11 Throttle valve absolute opening angle %

EN(H4DOTC 2.5)-30
ENGINE (DIAGNOSTIC)
Subaru Select Monitor
5. READ CURRENT DATA FOR ENGINE (OBD MODE)
1) On the «Main Menu» display screen, select the {Each System Check} and press the [YES] key.
2) On the «System Selection Menu» display screen, select the {Engine} and press the [YES] key.
3) Press the [YES] key after the information of engine type was displayed.
4) On the «Engine Diagnosis» display screen, select the {OBD System} and press the [YES] key.
5) On the «OBD Menu» screen, select the {Current Data Display/Save}, and then press the [YES] key.
6) On the «Data Display Menu» screen, select the {Data Display} and press the [YES] key.
7) Using the scroll key, move the display screen up or down until the desired data is shown.
 A list of the support data is shown in the following table.
NOTE:
For detailed operation procedure, refer to the “SUBARU SELECT MONITOR OPERATION MANUAL”.
Description Display Unit of measure
Number of diagnosis code Number of Diagnosis Code —
Condition of malfunction indicator light MI (MIL) ON or OFF
Monitoring test of misfire Misfire monitoring No support
Monitoring test of fuel system Fuel system monitoring No support
Monitoring test of comprehensive component Component monitoring No support
Test of catalyst Catalyst Diagnosis No support
Test of heating-type catalyst Heated catalyst No support
Test of evaporative emission purge control system Evaporative purge system No support
Test of secondary air system Secondary air system No support
Test of air conditioning system refrigerant A/C system refrigerant No support
Test of oxygen sensor Oxygen sensor No support
Test of oxygen sensor heaterO
2 Heater Diagnosis
No support
Test of EGR system EGR system No support
Air fuel ratio control system for bank 1 Fuel System for Bank 1 —
Engine load data Calculated load value %
Engine coolant temperature signal Coolant Temp.°C or °F
Short term fuel trim by front oxygen (A/F) sensor Short term fuel trim B1 %
Long term fuel trim by front oxygen (A/F) sensor Long term fuel trim B1 %
Intake manifold absolute pressure signal Mani. Absolute Pressure mmHg, kPa, inHg or psi
Engine speed signal Engine Speed rpm
Vehicle speed signal Vehicle Speed km/h or MPH
Ignition timing advance for #1 cylinder Ignition timing adv. #1°
Intake air temperature signal Intake Air Temp.°C or °F
Amount of intake air Mass Air Flow g/s
Throttle position signal Throttle Opening Angle %
Oxygen sensor #11 Oxygen Sensor #11 —
Oxygen sensor #12 Oxygen Sensor #12 —
Rear oxygen sensor output signal Oxygen Sensor #12 V
Air fuel ratio correction by rear oxygen sensor Short term fuel trim #12 %
On-board diagnostic system OBD System others
A/F sensor output signal A/F sensor #11 V
A/F lambda signal A/F sensor #11 —
A/F lambda signal #11 A/F sensor #11 —
A/F sensor current #11 A/F sensor #11 mA

EN(H4DOTC 2.5)-32
ENGINE (DIAGNOSTIC)
Subaru Select Monitor
7. LED OPERATION MODE FOR ENGINE
1) On the «Main Menu» display screen, select the {Each System Check} and press the [YES] key.
2) On the «System Selection Menu» display screen, select the {Engine} and press the [YES] key.
3) Press the [YES] key after the information of engine type was displayed.
4) On the «Engine Diagnosis» screen, select the {Current Data Display/Save}, and then press the [YES] key.
5) On the «Data Display» screen, select the {Data & LED Display} and press the [YES] key.
6) Using the scroll key, move the display screen up or down until the desired data is shown.
 A list of the support data is shown in the following table.
Description Display Message LED “ON” requirements
Ignition switch signal Ignition Switch ON or OFF When ignition switch is ON.
Test Mode Signal Test Mode Signal ON or OFF When test mode connector is connected.
Neutral position switch signal Neutral Position Switch ON or OFF When neutral position signal is entered.
Air conditioning switch signal A/C Switch ON or OFF When air conditioning switch is ON.
Air conditioning relay signal A/C Compressor Signal ON or OFF When air conditioning relay is in function.
Radiator main fan relay signal Radiator Fan Relay #1 ON or OFF When radiator main fan relay is in function.
Knocking signal Knocking Signal ON or OFF When knocking signal is input.
Radiator sub fan relay signal Radiator Fan Relay #2 ON or OFF When radiator sub fan relay is in function.
Rear oxygen sensor rich signalRear O
2 Rich Signal
ON or OFFWhen rear oxygen sensor mixture ratio is
rich.
Starter switch signal Starter Switch Signal ON or OFF When starter switch signal is entered.
Idle switch signal Idle Switch Signal ON or OFF When idle switch signal is entered.
Crankshaft position sensor signal Crankshaft Position Signal ON or OFFWhen crankshaft position sensor signal is
input.
Camshaft position sensor signal Camshaft Position Signal ON or OFFWhen camshaft position sensor signal is
entered.
Power steering switch signal P/S Switch ON or OFF When power steering switch is entered.
Rear defogger switch signal Rear Defogger Switch ON or OFF When rear defogger switch is ON.
Blower fan switch signal Blower Fan Switch ON or OFF When blower fan switch is ON.
Small light switch signal Light Switch ON or OFF When small light switch is ON.
Tumble generated valve actuator
signalTGV Output ON or OFF When TGV actuator signal is entered.
Tumble generated valve drive sig-
nalTGV DriveClose or
OpenWhen TGV moves and valve opens.
Handle switch signal Handle SWLow Input
or High
InputIlluminates in Low Input.
AT/MT identification terminal AT Vehicle ID Signal ON or OFF ON (AT model).
Wiper switch signal Wiper Switch ON or OFF When wiper switch is turned to ON.
A/C mid pressure switch signal A/C Mid Pressure Switch ON or OFFWhen A/C mid pressure switch is turned to
ON.
AT coordinate retard angle
demandRetard Signal from AT ON or OFF When AT retard angle signal is exists.
AT coordinate fuel cut demand Fuel Cut Signal from AT ON or OFFWhen AT coordinate fuel cut demand signal
is exists.
AT coordinate permission signal Torque Permission Signal ON or OFFWhen AT coordinate permission signal is
exists.
VDC not torque down out put Ban of Torque Down ON or OFFWhen VDC not torque down output signal is
exists.
VDC torque down demand Request Torque Down VDC ON or OFFWhen VDC torque down demand signal is
exists.
ETC motor relay signal ETC Motor Relay ON or OFFWhen electronic throttle control relay is in
function.
Clutch switch signal Clutch Switch ON or OFF When clutch switch is ON.
Stop switch signal Stop Light Switch ON or OFF When stop light switch is ON.

EN(H4DOTC 2.5)-38
ENGINE (DIAGNOSTIC)
Inspection Mode
5) Connect the Subaru Select Monitor to data link
connector located in the lower portion of the instru-
ment panel (on the driver’s side).
CAUTION:
Do not connect the scan tools except for Suba-
ru Select Monitor and OBD-II general scan tool.
6) Turn the ignition switch to ON (engine OFF) and
Subaru Select Monitor switch to ON.
7) On the «Main Menu» display screen, select the
{Each System Check} and press the [YES] key.
8) On the «System Selection Menu» display screen,
select the {Engine} and press the [YES] key.
9) Press the [YES] key after the information of en-
gine type was displayed.
10) On the «Engine Diagnosis» screen, select the
{D Check} and press the [YES] key.
11) When the “Perform D Check?” is shown on the
screen, press the [YES] key.
12) Perform subsequent procedures as instructed
on the display screen.
 If trouble still remains in the memory, the corre-
sponding DTC appears on the display screen.
NOTE:
 For detailed operation procedure, refer to the “SUB-
ARU SELECT MONITOR OPERATION MANUAL”.
 For details concerning DTCs, refer to the List of
Diagnostic Trouble Code (DTC).
Trouble Code (DTC).>
 Release the parking brake. The speed difference between front and rear
wheels may light either the ABS warning light, but this
indicates no malfunctions. When engine control diag-
nosis is finished, perform the ABS memory clearance
procedure of self-diagnosis function. 23, Clear Memory Mode.>
3. OBD-II GENERAL SCAN TOOL
1) Idle the engine.
2) Connect the test mode connector (A) located at
the lower portion of instrument panel (on the driv-
er’s side).
3) Connect the OBD-II general scan tool to its data
link connector in the lower portion of the instrument
panel (on the driver’s side).
CAUTION:
Do not connect the scan tools except for Suba-
ru Select Monitor and OBD-II general scan tool.
4) Start the engine.
NOTE:
 Ensure the select lever is placed in the “P” range
before starting. (AT model)
 Depress the clutch pedal when starting the en-
gine. (MT model)
5) Using the select lever or shift lever, turn the “P”
position switch and the “N” position switch to ON.
6) Depress the brake pedal to turn the brake switch
ON. (AT model)
7) Keep the engine speed in the 2,500 — 3,000
rpm range for 40 seconds.
8) Place the select lever or shift lever in the “D”
range (AT model) or “1st” gear (MT model) and
drive the vehicle at 5 to 10 km/h (3 to 6 MPH).
(A) Power switch
EN-02353
EN-00040
(A)
EN-00333
(A)
EN-02353

EN(H4DOTC 2.5)-39
ENGINE (DIAGNOSTIC)
Inspection Mode
NOTE:
 On AWD vehicles, release the parking brake.
 The speed difference between front and rear
wheels may light either the ABS warning light, but
this indicates no malfunctions. When engine con-
trol diagnosis is finished, perform the ABS memory
clearance procedure of self-diagnosis function.

9) Using the OBD-II general scan tool, check
DTC(s) and record the result(s).
NOTE:
 For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.
 For details concerning DTCs, refer to the List of
Diagnostic Trouble Code (DTC).
Trouble Code (DTC).>

EN(H4DOTC 2.5)-45
ENGINE (DIAGNOSTIC)
Malfunction Indicator Light
15.Malfunction Indicator Light
A: PROCEDURE
B: ACTIVATION OF MALFUNCTION
INDICATOR LIGHT
1) When the ignition switch is turned to ON (engine
off), the malfunction indicator light in the combina-
tion meter illuminates.
NOTE:
If the malfunction indicator light does not illuminate,
perform the diagnosis of malfunction indicator light
circuit or the combination meter circuit. EN(H4DOTC 2.5)-47, MALFUNCTION INDICA-
TOR LIGHT DOES NOT COME ON, Malfunction
Indicator Light.>2) After starting the engine, the malfunction indica-
tor light goes out. If it does not, either the engine or
the emission control system is malfunctioning.
1. Activation of malfunction indicator light. Malfunction Indicator Light.>
↓
2. Check that the malfunction indicator light does not come on. LIGHT DOES NOT COME ON, Malfunction Indicator Light.>
↓
3. Check that the malfunction indicator light does not go off. DOES NOT GO OFF, Malfunction Indicator Light.>
↓
4. Malfunction indicator light does not blink at a cycle of 3 Hz. DOES NOT BLINK AT A CYCLE OF 3 HZ, Malfunction Indicator Light.>
↓
5. Malfunction indicator light remains blinking at a cycle of 3 Hz. LIGHT REMAINS BLINKING AT A CYCLE OF 3 HZ, Malfunction Indicator Light.>
(A) Malfunction indicator light
EN-00335(A)
(1) No faulty
(2) Trouble occurs
(3) ON
(4) OFF
(5) Ignition switch ON
(6) Engine start
EN-01679
(1)
(2)
(5)
(6)(3)
(4)
(3)
(4)

EN(H4DOTC 2.5)-48
ENGINE (DIAGNOSTIC)
Malfunction Indicator Light
Step Check Yes No
1 CHECK OUTPUT SIGNAL FROM ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 17 (+) — Chassis ground (
−):Is the voltage less than 1 V? Go to step 4.Go to step 2.
2 CHECK POOR CONTACT.Does the malfunction indicator
light come on when shaking or
pulling the ECM connector and
harness?Repair the poor
contact in ECM
connector.Go to step 3.
3 CHECK ECM CONNECTOR.Is the ECM connector correctly
connected?Replace the ECM.
FU(H4DOTC 2.5)-
41, Engine Con-
trol Module
(ECM).>Repair the con-
nection of ECM
connector.
4 CHECK HARNESS BETWEEN COMBINA-
TION METER AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the combination meter. IDI-10, Combination Meter Assembly.>
3) Disconnect the connector from ECM and
combination meter.
4) Measure the resistance of harness between
ECM and combination meter connector.
Connector & terminal
(B134) No. 17 — (i12) No. 1:Is the resistance less than 1
Ω?Go to step 5.Repair the harness
and connector.
NOTE:
In this case repair
the following:
 Open circuit in
harness between
ECM and combi-
nation meter con-
nector
 Poor contact in
coupling connector
5 CHECK POOR CONTACT.
Check poor contact in combination meter con-
nector.Is there poor contact in combi-
nation meter connector?Repair poor con-
tact in combination
meter connector.Go to step 6.
6 CHECK HARNESS BETWEEN COMBINA-
TION METER AND IGNITION SWITCH CON-
NECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between combination
meter connector and chassis ground.
Connector & terminal
(i10) No. 9 (+) — Chassis ground (
−):Is the voltage more than 10 V? Replace the board
of combination
meter. 10, Combination
Meter Assembly.>Check the follow-
ing and repair if
necessary.
N
OTE:
 Blown out of
fuse (No. 14)
 Open or short
circuit in harness
between fuse (No.
14) and battery
terminal
 Poor contact in
ignition switch con-
nector

EN(H4DOTC 2.5)-49
ENGINE (DIAGNOSTIC)
Malfunction Indicator Light
D: MALFUNCTION INDICATOR LIGHT DOES NOT GO OFF
DIAGNOSIS:
The malfunction indicator light circuit is shorted.
TROUBLE SYMPTOM:
Although malfunction indicator light comes on when the engine runs, DTC is not shown on the Subaru Select
Monitor or OBD-II general scan tool display.
WIRING DIAGRAM:
Step Check Yes No
1 CHECK HARNESS BETWEEN COMBINA-
TION METER AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Turn the ignition switch to ON.Does malfunction indicator
light illuminate?Repair short circuit
in harness
between combina-
tion meter and
ECM connector.Replace the ECM.
FU(H4DOTC 2.5)-
41, Engine Con-
trol Module
(ECM).>
EN-02354
SBF-4 SBF-1
No.14B72
B38
B134ECMi3
E
1 4
17
i12 A:
i10 B:B9
A1
B72 i12 i10
i3
3412
123 456
789 121310 11 14
13
i3 B38
A: B: COMBINATION
METERIGNITION
SWITCHBATTERY
B134
56 7
82 1
94 3
10
24 22 23 25 11 12 13 14 15
26 27
2816 17
18 19 20 21
33 34 29
32 30 31
16
219
32
1234 5610 11 12 13 14 15716
23 3019 20
22 26 27 28 29817
24 3118
25
123456789101112131415161718192021222324252627282930

EN(H4DOTC 2.5)-51
ENGINE (DIAGNOSTIC)
Malfunction Indicator Light
Step Check Yes No
1 CHECK STATUS OF MALFUNCTION INDI-
CATOR LIGHT.
1) Turn the ignition switch to OFF.
2) Disconnect the test mode connectors.
3) Turn the ignition switch to ON. (engine OFF)Does malfunction indicator
light illuminate?Go to step 2.Repair the malfunc-
tion indictor light cir-
cuit. EN(H4DOTC 2.5)-
47, MALFUNC-
TION INDICA-
TOR LIGHT
DOES NOT
COME ON, Mal-
function Indicator
Light.>
2 CHECK HARNESS BETWEEN COMBINA-
TION METER AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Turn the ignition switch to ON.Does malfunction indicator
light illuminate?Repair ground
short circuit in har-
ness between com-
bination meter and
ECM connector.Go to step 3.
3 CHECK HARNESS BETWEEN TEST MODE
CONNECTOR AND CHASSIS GROUND.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between test mode connector and chassis
ground.
Connector & terminal
(B76) No. 1 — Chassis ground:Is the resistance less than 1
Ω?Go to step 4.Repair the harness
and connector.
N
OTE:
In this case repair
the following:
 Open circuit in
harness between
test mode connec-
tor and chassis
ground
4 CHECK POOR CONTACT.
Check poor contact in ECM connector.Is there poor contact in ECM
connector?Repair the poor
contact in ECM
connector.Go to step 5.
5 CHECK HARNESS BETWEEN ECM AND
TEST MODE CONNECTOR.
1) Connect the test mode connector.
2) Measure the resistance of harness
between ECM and chassis ground.
Connector & terminal
(B137) No. 15 — Chassis ground:Is the resistance less than 1
Ω?Go to step 6.Repair open circuit
in harness between
ECM and test
mode connector.
6 CHECK POOR CONTACT.
Check poor contact in ECM connector.Is there poor contact in ECM
connector?Repair the poor
contact in ECM
connector.Replace the ECM.
FU(H4DOTC 2.5)-
41, Engine Con-
trol Module
(ECM).>