Subaru Impreza 2004 User manual

FUJI HEAVY INDUSTRIES LTD. G1870GE3
2004 IMPREZA SERVICE MANUAL QUICK REFERENCE INDEX
ENGINE SECTION 2
This service manual has been prepared
to provide SUBARU service personnel
with the necessary information and data
for the correct maintenance and repair
of SUBARU vehicles.
This manual includes the procedures
for maintenance, disassembling, reas-
sembling, inspection and adjustment of
components and diagnostics for guid-
ance of experienced mechanics.
Please peruse and utilize this manual
fully to ensure complete repair work for
satisfying our customers by keeping
their vehicle in optimum condition.
When replacement of parts during
repair work is needed, be sure to use
SUBARU genuine parts.
All information, illustration and specifi-
cations contained in this manual are
based on the latest product information
available at the time of publication
approval.
FUEL INJECTION (FUEL SYSTEMS) FU(H4DOTC)
EMISSION CONTROL
(AUX. EMISSION CONTROL DEVICES) EC(H4DOTC)
INTAKE (INDUCTION) IN(H4DOTC)
MECHANICAL ME(H4DOTC)
EXHAUST EX(H4DOTC)
COOLING CO(H4DOTC)
LUBRICATION LU(H4DOTC)
SPEED CONTROL SYSTEMS SP(H4DOTC)
IGNITION IG(H4DOTC)
STARTING/CHARGING SYSTEMS SC(H4DOTC)
ENGINE (DIAGNOSTICS) EN(H4DOTC)(diag)

ENGINE (DIAGNOSTICS)
EN(H4DOTC)(diag)
Page
1. Basic Diagnostic Procedure ........................................................................2
2. Check List for Interview...............................................................................4
3. General Description ....................................................................................6
4. Electrical Components Location..................................................................9
5. Engine Control Module (ECM) I/O Signal .................................................23
6. Engine Condition Data ..............................................................................27
7. Transmission Control Module (TCM) I/O Signal .......................................28
8. Data Link Connector .................................................................................29
9. OBD-II General Scan Tool ........................................................................30
10. Subaru Select Monitor...............................................................................32
11. Read Diagnostic Trouble Code (DTC) ......................................................38
12. Inspection Mode........................................................................................39
13. Drive Cycle................................................................................................45
14. Clear Memory Mode..................................................................................47
15. Compulsory Valve Operation Check Mode ...............................................48
16. Malfunction Indicator Light ........................................................................50
17. Diagnostics for Engine Starting Failure.....................................................59
18. List of Diagnostic Trouble Code (DTC) .....................................................74
19. Diagnostic Procedure with Diagnostic Trouble Code (DTC) .....................81
20. General Diagnostic Table........................................................................308

EN(H4DOTC)(diag)-2
ENGINE (DIAGNOSTICS)
Basic Diagnostic Procedure
1. Basic Diagnostic Procedure
A: PROCEDURE
1. ENGINE
Step Check Yes No
1 CHECK ENGINE START FAILURE.
1)Ask the customer when and how trouble
occurred using the interview check list. <Ref.
to EN(H4DOTC)(diag)-4, CHECK, Check List
for Interview.>
2)Start the engine.
Does the engine start? Go to step 2. Inspection using
“Diagnostics for
Engine Start Fail-
ure”. <Ref. to
EN(H4DOTC)(dia
g)-59, Diagnostics
for Engine Start-
ing Failure.>
2 CHECK ILLUMINATION OF MALFUNCTION
INDICATOR LIGHT.
Does the malfunction indicator
light illuminate?
Go to step 3. Inspection using
“General Diagnos-
tics Table”. <Ref.
to
EN(H4DOTC)(dia
g)-308, General
Diagnostic Table.>
3 CHECK INDICATION OF DTC ON DISPLAY.
1)Turn the ignition switch to OFF.
2)Connect the Subaru Select Monitor or OBD-
II general scan tool to data link connector.
3)Turn the ignition switch to ON and the Sub-
aru Select Monitor or OBD-II general scan tool
switch to ON.
4)Read the DTC on Subaru Select Monitor or
OBD-II general scan tool.
Does the Subaru Select Moni-
tor or OBD-II general scan tool
indicate DTC?
Record the DTC
code. Repair the
trouble cause.
<Ref. to
EN(H4DOTC)(dia
g)-74, List of Diag-
nostic Trouble
Code (DTC).> Go
to step 4.
Repair the related
parts.
N
O
TE:
If a DTC is not
shown on display
although malfunc-
tion indicator light
illuminates, per-
form diagnostics of
malfunction indica-
tor light circuit or
combination
meter. <Ref. to
EN(H4DOTC)(di-
ag)-50, Malfunc-
tion Indicator
Light.>
4 PERFORM THE DIAGNOSIS.
1)Perform the clear memory mode. <Ref. to
EN(H4DOTC)(diag)-47, Clear Memory Mode.>
2)Perform the inspection mode. <Ref. to
EN(H4DOTC)(diag)-39, Inspection Mode.>
Does the Subaru Select Moni-
tor or OBD-II general scan tool
indicate DTC?
Inspect using
“Diagnostics Pro-
cedure with Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(H4DOTC)(dia
g)-81, Diagnostic
Procedure with
Diagnostic Trou-
ble Code (DTC).>
Complete the
diagnosis.

EN(H4DOTC)(diag)-3
ENGINE (DIAGNOSTICS)
Basic Diagnostic Procedure
2. AUTOMATIC TRANSMISSION
When DTC about automatic transmission is shown
on display, carry out the following basic check. Af-
ter that, carry out the replacement or repair work.
1) ATF level check <Ref. to 4AT-31, Automatic
Transmission Fluid.>
2) Differential gear oil level check <Ref. to 4AT-33,
Differential Gear Oil.>
3) ATF leak check <Ref. to 4AT-31, Automatic
Transmission Fluid.>
4) Differential gear oil leak check <Ref. to 4AT-33,
Differential Gear Oil.>
5) Stall test <Ref. to 4AT-35, Stall Test.>
6) Line pressure test <Ref. to 4AT-38, Line Pres-
sure Test.>
7) Transfer clutch pressure test <Ref. to 4AT-39,
Transfer Clutch Pressure Test.>
8) Time lag test <Ref. to 4AT-37, Time Lag Test.>
9) Road test <Ref. to 4AT-34, Road Test.>
10) Shift characteristics <Ref. to 4AT-39, Transfer
Clutch Pressure Test.>

EN(H4DOTC)(diag)-4
ENGINE (DIAGNOSTICS)
Check List for Interview
2. Check List for Interview
A: CHECK
1. CHECK LIST No. 1
Check the following items when problem has occurred.
NOTE:
Use copies of this page for interviewing customers.
Customer’s name Engine No.
Date of sale Fuel brand
Date of repair Odometer reading km
VIN miles
Weather ❏Fine
❏Cloudy
❏Rainy
❏Snowy
❏Various/Others:
Outdoor temperature °C (°F)
❏Hot
❏Warm
❏Cool
❏Cold
Place ❏Highway
❏Suburbs
❏Inner city
❏Uphill
❏Downhill
❏Rough road
❏Others:
Engine temperature ❏Cold
❏Warming-up
❏After warming-up
❏Any temperature
❏Others:
Engine speed rpm
Vehicle speed km/h (MPH)
Driving conditions ❏Not affected
❏At starting
❏While idling
❏At racing
❏While accelerating
❏While cruising
❏While decelerating
❏While turning (RH/LH)
Headlight ❏ON / ❏OFF Rear defogger ❏ON / ❏OFF
Blower ❏ON / ❏OFF Radio ❏ON / ❏OFF
A/C compressor ❏ON / ❏OFF CD/Cassette ❏ON / ❏OFF
Cooling fan ❏ON / ❏OFF Car phone ❏ON / ❏OFF
Front wiper ❏ON / ❏OFF CB ❏ON / ❏OFF
Rear wiper ❏ON / ❏OFF

EN(H4DOTC)(diag)-5
ENGINE (DIAGNOSTICS)
Check List for Interview
2. CHECK LIST No. 2
Check the following items about the vehicle’s state when malfunction indicator light turns on.
NOTE:
Use copies of this page for interviewing customers.
a) Other warning lights or indicators turn on. ❏Yes / ❏No
❏Low fuel warning light
❏Charge indicator light
❏AT diagnostics indicator light
❏ABS warning light
❏Engine oil pressure warning light
b) Fuel level
•Lack of gasoline: ❏Yes / ❏No
•Indicator position of fuel gauge:
•Experienced running out of fuel: ❏Yes / ❏No
c) Intentional connecting or disconnecting of harness connectors or spark plug cords: ❏Yes / ❏No
•What:
d) Intentional connecting or disconnecting of hoses: ❏Yes / ❏No
•What:
e) Installing of parts other than genuine parts: ❏Yes / ❏No
•What:
•Where:
f) Occurrence of noise: ❏Yes / ❏No
•From where:
•What kind:
g) Occurrence of smell: ❏Yes / ❏No
•From where:
•What kind:
h) Intrusion of water into engine compartment or passenger compartment: ❏Yes / ❏No
i) Troubles occurred
❏Engine does not start.
❏Engine stalls during idling.
❏Engine stalls while driving.
❏Engine speed decreases.
❏Engine speed does not decrease.
❏Rough idling
❏Poor acceleration
❏Back fire
❏After fire
❏No shift
❏Excessive shift shock

EN(H4DOTC)(diag)-6
ENGINE (DIAGNOSTICS)
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 colored yellow. Do not use the elec-
trical test equipment on these circuit.
•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 instantly.
•The fuel injector and other part will be damaged
in just a few minutes more.
3) Do not disconnect the battery cables while the
engine is running.
•A large counter electromotive force will be gener-
ated in the alternator, 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 the ignition
switch to OFF.
5) Poor contact has been identified as a primary
cause of this problem. To measure the voltage and/
or resistance of individual sensors or all electrical
control modules at the harness side connector, use
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) Before removing the ECM from located position,
disconnect 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 any damage on
the fuel injection system.
7) The connectors to each sensor in the engine
compartment and the harness connectors on the
engine side and body side are all designed to be
waterproof. However, it is still necessary to take
care not to allow water to get into the connectors
when washing the vehicle, or when servicing the
vehicle on a rainy day.
8) Use the ECM mounting stud bolt at the body
head grounding points when measuring voltage
and resistance inside the passenger compartment.
9) Use the engine grounding terminal or engine
proper as the grounding point to the body, when
measuring voltage and resistance in the engine
compartment.
10) Use the TCM mounting stud bolts at the
grounding point, when measuring voltage and re-
sistance inside the passenger compartment.
11) Every MFI-related part is a precision part. Do
not drop them.
(A) Stud bolt
(A) Stud bolt
EN-00069
(A)
EN-00070
EN-00071
(A)

EN(H4DOTC)(diag)-7
ENGINE (DIAGNOSTICS)
General Description
12) 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 as
possible from ECM and MFI harness.
•Carefully adjust the antenna for correct
matching.
•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 ECM.
13) Before disconnecting the fuel hose, disconnect
the fuel pump connector and crank the engine for
more than 5 seconds to release pressure in the fuel
system. If the engine starts during this operation,
run it until it stops.
14) Problems in the electronic-controlled automatic
transmission may be caused by failure of the en-
gine, the electronic control system, the transmis-
sion proper, or by a combination of these. These
three causes must be distinguished clearly when
performing diagnostics.
15) 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.
16) On model with ABS, when performing driving
test in jacked-up or lifted-up position, sometimes
the warning light may be lit, but this is not a mal-
function of the system. The reason for this is the
speed difference between front and rear wheels.
After diagnosis of engine control system, perform
the ABS memory clearance procedure of self-diag-
nosis system.
B: INSPECTION
Before performing diagnostics, check the following
items which might affect engine problems:
1. BATTERY
1) Measure the battery voltage and specific gravity
of electrolyte.
Standard voltage: 12 V
Specific gravity: Above 1.260
2) Check the condition of main and other fuses,
and harnesses and connectors. Also check for
proper grounding.
2. ENGINE GROUNDING
Make sure the engine grounding terminal is proper-
ly connected to engine.
C: NOTE
1. DESCRIPTION
•The on-board diagnostics (OBD) system detects
and indicates a fault in various inputs and outputs
of complex electronic control. Malfunction indicator
light in 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 malfunction indicator light illumination
or blinking, a DTC and a freeze frame engine con-
ditions 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.
EN-00070

EN(H4DOTC)(diag)-8
ENGINE (DIAGNOSTICS)
General Description
•The OBD-II diagnostics procedure is different
from usual diagnostics procedure. When trouble-
shooting model with OBD-II, connect the Subaru
Select Monitor or the OBD-II general scan tool to
the vehicle.
2. ENGINE AND EMISSION CONTROL SYS-
TEM
•The Multipoint Fuel Injection (MFI) system is a
system that supplies the optimum air-fuel mixture
to the engine for all the various operating condi-
tions through the use of the latest electronic tech-
nology.
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
pulse 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.
•Superior startability and warm-up perfor-
mance in cold weather since compensation is
made for coolant and intake air temperature.
D: PREPARATION TOOL
ILLUSTRATION TOOL NUMBER DESCRIPTION REMARKS
24082AA230 CARTRIDGE Troubleshooting for electrical systems.
22771AA030 SUBARU SELECT
MONITOR KIT
Troubleshooting for electrical systems.
•English: 22771AA030 (Without printer)
•German: 22771AA070 (Without printer)
•French: 22771AA080 (Without printer)
•Spanish: 22771AA090 (Without printer)
ST24082AA230
ST22771AA030

EN(H4DOTC)(diag)-9
ENGINE (DIAGNOSTICS)
Electrical Components Location
4. Electrical Components Location
A: LOCATION
1. ENGINE
•Module
(1) Engine control module (ECM) (3) Test mode connector (4) Data link connector
(2) Malfunction indicator light
EN-01269
(1)
(2)
(3) (4)
EN-01270
(1)
(2)
(3) (4)

EN(H4DOTC)(diag)-10
ENGINE (DIAGNOSTICS)
Electrical Components Location
EN-00156 EN-01271
(2)
EN-01272
(3)
EN-01150
(4)

EN(H4DOTC)(diag)-11
ENGINE (DIAGNOSTICS)
Electrical Components Location
•Sensor
(1) Manifold absolute pressure sensor (4) Knock sensor (7) Mass air flow and intake air tem-
perature sensor
(2) Engine coolant temperature sen-
sor
(5) Camshaft position sensor
(6) Crankshaft position sensor (8) Tumble generator valve position
sensor
(3) Throttle position sensor
EN-01274
(7) (3)
(6) (8) (5)(4)
(1)(2)(8)

EN(H4DOTC)(diag)-12
ENGINE (DIAGNOSTICS)
Electrical Components Location
(1)
EN-00294
(2)
EN-00295
(3)
EN-00296 EN-00297
(4)
EN-00298
(5)
EN-00299
(6)
(7)
EN-00300
(8)
EN-00301

EN(H4DOTC)(diag)-13
ENGINE (DIAGNOSTICS)
Electrical Components Location
•Except for Australia model
•For Australia model except for STi
(1) Front oxygen (A/F) sensor (4) Front catalytic converter (6) Rear catalytic converter
(2) Precatalytic converter (Except for
Australia model and STi model)
(5) Rear oxygen sensor (Except for
Australia model)
(7) Rear oxygen sensor (Australia
model except for STi)
(3) Exhaust temperature sensor
(Except for Australia model and
STi model)
(1)
(4)
(3)
(5) (6)
(2)
EN-00302
EN-01275
(1)
(4)
(7)
(6)

EN(H4DOTC)(diag)-14
ENGINE (DIAGNOSTICS)
Electrical Components Location
(1)
EN-00303 EN-00304
(3)
(2)
(4)
EN-00305
(5)
EN-00306
(6)
EN-00307 EN-01568
(7)

EN(H4DOTC)(diag)-15
ENGINE (DIAGNOSTICS)
Electrical Components Location
(1) Fuel level sensor (2) Fuel sub level sensor
EN-01276
(1)
(2)
EN-01277
(1)
(2)
EN-00310
(1)
EN-00311
(2)

EN(H4DOTC)(diag)-16
ENGINE (DIAGNOSTICS)
Electrical Components Location
•Solenoid Valve, Actuator, Emission Control System Parts and Ignition System Parts
(1) Wastegate control solenoid valve (3) Purge control solenoid valve (5) Tumble generator valve actuator
(2) Idle air control solenoid valve (4) Ignition coil
EN-01278
(1) (5)
(5) (3)
(2)
(4)

EN(H4DOTC)(diag)-17
ENGINE (DIAGNOSTICS)
Electrical Components Location
EN-00313
(1) EN-00314
(2)
EN-00315
(3)
EN-00316
(4)
(5)
EN-00317

EN(H4DOTC)(diag)-18
ENGINE (DIAGNOSTICS)
Electrical Components Location
(1) Fuel pump (5) Fuel pump control unit (9) Radiator sub fan relay 2
(2) Inhibitor switch (6) Radiator main fan relay 1 (10) Starter
(3) Main relay (7) Radiator main fan relay 2
(4) Fuel pump relay (8) Radiator sub fan relay 1
EN-01279
(3) (4) (1) (5)
(8)
(7) (10)
(9)
(6)
(2)
EN-01280
(3) (4)
(1) (5)
(8)
(7) (10)
(9)
(6)
(2)

EN(H4DOTC)(diag)-19
ENGINE (DIAGNOSTICS)
Electrical Components Location
(1)
EN-00320 (2) EN-00321
(4)
(3)
EN-01281
(5)
EN-01282
EN-01596
(7)
(8)
(6)
(9)
EN-01328
(10)