Subaru IMPREZA GD 2007 Series Manual page 115

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ENGINE (DIAGNOSTICS)
B: INSPECTION
Before performing diagnostics, check the following
item which might affect engine problems.
1. BATTERY
1) Measure the battery voltage and specific gravity
of the electrolyte.
Standard voltage: 12 V
Specific gravity: 1.260 or more
2) Check the condition of the main and other fuses,
and harnesses and connectors. Also check for
proper grounding.
2. ENGINE GROUND
Check if the engine ground terminal is properly
connected to engine.
C: NOTE
1. GENERAL DESCRIPTION
• The on-board diagnostic (OBD) system detects
and indicates a fault in various inputs and outputs
of the complex electronic control. Malfunction indi-
cator light in the combination meter indicates oc-
currence 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 type of engine complies with OBD-II reg-
ulations. 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, a DTC and a freeze frame en-
gine conditions are stored into on-board computer.
General Description
• 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 first when it
detects a malfunction.
• If the OBD system detects malfunctions such as
the fault of fuel trim or misfire, the OBD system first
stores freeze frame engine conditions 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.
• When troubleshooting the vehicle which com-
plies with OBD-II regulations, connect the Subaru
Select Monitor or 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, the fuel which is pressurized at a
constant pressure is injected into the intake air pas-
sage of the cylinder head. The injection quantity of
fuel is controlled by an intermittent injection sys-
FU-01090
tem, where the electro-magnetic injection valve (fu-
el injector) opens for a short period of time
depending on the quantity of air required for one
cycle of operation. In actual operation, the injection
quantity 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.
• Furthermore, all operating conditions of the en-
gine are converted into electronic signals, and this
enables additional system features with greatly im-
proved adaptability, making it easier to add com-
pensation features.
The MFI system also has the following features:
• Reduced emission of harmful exhaust gases.
• Reduction 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 engine coolant and intake air tempera-
ture.
EN(H4SO)(diag)-6