Subaru 2006 Legacy, Manual

Page: 912 / 4302

EN(H4SO U5)(diag)-7
General Description
ENGINE (DIAGNOSTICS)
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. 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 engine family 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.
• 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 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.
• 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-
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.
• 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.
• 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.
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