2004 SUBARU FORESTER engine

EN(H4DOTC 2.5)-5
ENGINE (DIAGNOSTIC)
General Description
3. General Description
A: CAUTION
1) Airbag system wiring harness is routed near the
ECM, main relay and fuel pump relay.
CAUTION:
 All airbag system wiring harness and con-
nectors are all colored yellow. Do not use the
electrical test equipment on these circuits.
 Be careful not to damage the Airbag system
wiring harness when servicing the ECM, TCM,
main relay and fuel pump relay.
2) Never connect the battery in reverse polarity.
 The ECM will be destroyed immediately.
 The fuel injector and other part will be damaged.
3) Do not disconnect the battery terminals while the
engine is running.
 A large counter electromotive force will be gener-
ated in the generator, and this voltage may damage
electronic parts such as ECM, etc.
4) Before disconnecting the connectors of each
sensor and the ECM, be sure to turn OFF the igni-
tion switch.
5) Poor contact has been identified as a primary
cause of this problem. Measure the voltage or re-
sistance of individual sensor or all electrical control
modules using a tapered pin with a diameter of less
than 0.64 mm (0.025 in). Do not insert the pin more
than 5 mm (0.20 in) into the part.
6) Remove the ECM from the located position after
disconnecting two cables on battery.
 Otherwise, the ECM may be damaged.
CAUTION:
When replacing the ECM, be careful not to use
the wrong spec. ECM to avoid damaging the
fuel injection system.
7) Connectors to each sensor in the engine com-
partment and the harness connectors on the en-
gine side and body side are all designed to be
waterproof. However, take care not to allow water
to get into the connectors when washing the vehi-
cle, or when servicing the vehicle on a rainy day. 8) Use ECM mounting stud bolts on the body head
grounding point when measuring voltage and resis-
tance inside the passenger compartment.
9) Use engine ground terminal or engine proper as
the grounding point to the body when measuring
voltage and resistance in the engine compartment.
10) Every MFI-related part is a precision part. Do
not drop them.
11) Observe the following cautions when installing
a radio in MFI equipped models.
CAUTION:
 The antenna must be kept as far apart as pos-
sible from the control unit.
(The ECM is located under the steering column,
inside of the instrument panel lower trim panel.)
 The antenna feeder must be placed as far
apart as possible from the ECM and MFI har-
ness.
 Carefully adjust the antenna for correct match-
ing.
 When mounting a large power type radio, pay
special attention to the three items above men-
tioned.
 Incorrect installation of the radio may affect
the operation of the ECM.
12) Before disconnecting the fuel hose, disconnect
the fuel pump connector and crank the engine for
more than five seconds to release pressure in the
fuel system. If engine starts during this operation,
run it until it stops.
(A) Stud bolt
EN-00069
(A)
EN-01201

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)-7
ENGINE (DIAGNOSTIC)
General Description
2. ENGINE AND EMISSION CONTROL SYS-
TEM
 MFI system is a system that supplies the opti-
mum air-fuel mixture to the engine for all the vari-
ous operating conditions through the use of the
latest electronic technology.
With this system fuel, which is pressurized at a con-
stant pressure, is injected into the intake air pas-
sage of the cylinder head. The injection quantity of
fuel is controlled by an intermittent injection system
where the electro-magnetic injection valve (fuel in-
jector) opens only for a short period of time, de-
pending on the quantity of air required for one cycle
of operation. In actual operation, the injection quan-
tity is determined by the duration of an electric sig-nal applied to the fuel injector and this permits
simple, yet highly precise metering of the fuel.
 Further, all the operating conditions of the engine
are converted into electric signals, and this results
in additional features of the system, such as large
improved adaptability, easier addition of compen-
sating element, etc.
The MFI system also has the following features:
 Reduced emission of harmful exhaust gases.
 Reduced in fuel consumption.
 Increased engine output.
 Superior acceleration and deceleration.
 Excellent engine start and warm-up perfor-
mance by the correction of engine coolant tem-
perature and intake air temperature.
D: PREPARATION TOOL
ILLUSTRATION TOOL NUMBER DESCRIPTION REMARKS
24082AA230
(Newly adopted tool)CARTRIDGE Troubleshooting for electrical system.
22771AA030 SUBARU SELECT
MONITOR KITTroubleshooting for electrical system.
 English: 22771AA030 (Without printer)
 German: 22771AA070 (Without printer)
 French: 22771AA080 (Without printer)
 Spanish: 22771AA090 (Without printer)
ST24082AA230
ST22771AA030

EN(H4DOTC 2.5)-8
ENGINE (DIAGNOSTIC)
Electrical Component Location
4. Electrical Component Location
A: LOCATION
1. ENGINE
 CONTROL MODULE
(1) Engine control module (ECM) (3) Test Mode Connector (5) Data link connector
(2) Malfunction indicator light (4) Diagnosis connector
EN-00072
(3) (2)
(4) (1)(5)
EN-00235
(1)
(2)EN-00004
PI-00014
(4)
(3)
AT-00326 (5)

EN(H4DOTC 2.5)-9
ENGINE (DIAGNOSTIC)
Electrical Component Location
 SENSOR
(1) Manifold absolute pressure sen-
sor(3) Electronic throttle control (7) Mass air flow and intake air tem-
perature sensor
(4) Knock sensor
(2) Engine coolant temperature sen-
sor(5) Camshaft position sensor (8) Tumble generator valve position
sensor
(6) Crankshaft position sensor
EN-02008
(1)
(7) (6) (4) (8)(2)
(3)(5)

EN(H4DOTC 2.5)-10
ENGINE (DIAGNOSTIC)
Electrical Component Location
EN-02009
(3)
(1)
(2)
EN-00295
EN-00297 (4)EN-01798(5)
EN-00299 (6)
(7)
EN-00300
(8)
EN-00301

EN(H4DOTC 2.5)-11
ENGINE (DIAGNOSTIC)
Electrical Component Location
(1) Front oxygen (A/F) sensor (3) Exhaust gas temperature sensor (5) Rear oxygen sensor
(2) Precatalytic converter (4) Front catalytic converter (6) Rear catalytic converter
EN-02351 (1)
(5)
(6)
(4)
(2)(3)

EN(H4DOTC 2.5)-12
ENGINE (DIAGNOSTIC)
Electrical Component Location
(1) Fuel level sensor (2) Fuel sub level sensor
(1)
EN-00303EN-00304
(3)
(2)
(4)
EN-00305EN-02352
(5)
(6)
EN-00309(2)
(1)