OBD port SUBARU LEGACY 2004 4.G Owners Manual

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Starting and operating
obligation under federal law to implement stricter vehi-
cle emission standards to reduce air pollution from
cars. A dynamometer is a treadmill or roller-like testing
device that allows your car’s wheels to turn while the
car remains in one place. Depending on the severity of
a state’s air pollution problems, the states must adopt
either a “basic” or “enhanced” vehicle emission in-
spection test. Normally, a portion of the basic emission
test consists of an emission inspector inserting an an-
alyzer probe into the exhaust pipe of an idling vehicle
for a short period of time. States with more severe air
pollution problems are required to adopt an enhanced
vehicle emission test. This test simulates actual driv-
ing conditions on a dynamometer and permits more
accurate measurement of tailpipe emitted pollution
than the basic emission test.
The U.S. Environmental Protection Agency (EPA) and
states using two-wheel dynamometers in their emis-
sion testing programs have
EXEMPTED SUBARU
AWD vehicles from the portion of the testing program
that involves a two-wheel dynamometer.
There are some states that use four-wheel dynamom-
eters in their testing programs. When properly used,
that equipment will not damage an AWD SUBARU ve-
hicle.
Under no circumstances should the rear wheels be jacked off the ground, nor should the driveshaft be dis-
connected for state emission testing.
The EPA has issued regulations for inspecting the On-
Board Diagnostic (OBD) system as part of the state
emissions inspection. The OBD system is designed to
detect engine and transmission problems that might
cause vehicle emissions to exceed allowable limits.
These inspections apply to all 1996 model year and
newer passenger cars and light trucks. Several states
plus the District of Columbia have opted to start the
OBD system inspection prior to the required EPA reg-
ulation effective date of January 1, 2002. Other states
will add OBD system inspection in 2002. y
The inspection of the OBD system consists of a vi-
sual operational check of the “ CHECK ENGINE” warn-
ing light/malfunction indicator lamp (MIL) and an ex-
amination of the OBD system with an electronic scan
tool while the engine is running. y A vehicle passes
the OBD system inspection if
proper the “ CHECK ENGINE ” warning light/MIL illumi-
nation is observed, there is no stored diagnostic trou-
ble codes, and the OBD system readiness monitors
are complete. y A vehicle fails
the OBD inspection if the “ CHECK
ENGINE ” warning light/MIL is not properly operating
or there is one or more diagnostic trouble codes stored