Subaru 2002 IMPREZA Service Manual page 1166

ENGINE (DIAGNOSTICS)
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
apart as possible from the ECM and MFI har-
ness.
• 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 the 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 ABS vehicle, when performing driving test
in jacked-up or lifted-up position, sometimes the
warning light may be lit, but this is not a malfunction
of the system. The reason for this is the speed dif-
ference between the front and rear wheels. After di-
agnosis of engine control system, perform the ABS
memory clearance procedure of self-diagnosis sys-
tem.
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 the main and other fuses,
and harnesses and connectors. Also check for
proper grounding.
GENERAL DESCRIPTION
2. ENGINE GROUNDING
Make sure the engine grounding terminal is proper-
ly connected to the engine.
C: NOTE
1. DESCRIPTION
• The on-board diagnostics (OBD) system detects
and indicates a fault in various inputs and outputs
of the complex electronic control. CHECK ENGINE
malfunction indicator lamp (MIL) 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, MIL illuminates. At the same time of the MIL il-
lumination or blinking, a diagnostic trouble code
(DTC) and a freeze frame engine 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, MIL 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 diagnostics procedure. When trou-
bleshooting OBD-II vehicles, connect Subaru Se-
lect Monitor or the OBD-II general scan tool to the
vehicle.
EN(TURBO)-6
EN0945