Chevrolet 2003 Astro Owner's Manual page 156

This system is called OBD II (On-Board Diagnostics-
Second Generation) and is intended to assure that
emissions are at acceptable levels for the life of
the vehicle, helping to produce a cleaner environment.
The SERVICE ENGINE SOON or CHECK ENGINE
light comes on and a chime will sound to indicate that
there is a problem and service is required. Malfunctions
often will be indicated by the system before any
problem is apparent. This may prevent more serious
damage to your vehicle. This system is also designed to
assist your service technician in correctly diagnosing
any malfunction.
Notice: If you keep driving your vehicle with this
light on, after a while, your emission controls
may not work as well, your fuel economy may not
be as good and your engine may not run as
smoothly. This could lead to costly repairs that
may not be covered by your warranty.
Notice: Modifications made to the engine,
transmission, exhaust, intake or fuel system of
your vehicle or the replacement of the original tires
with other than those of the same Tire Performance
Criteria (TPC) can affect your vehicle's emission
controls and may cause this light to come on.
Modifications to these systems could lead to costly
repairs not covered by your warranty. This may
also result in a failure to pass a required Emission
Inspection/Maintenance test.
This light should come on, as a check to show you it
is working, when the ignition is on and the engine is not
running. If the light doesn't come on, have it repaired.
This light will also come on during a malfunction in one
of two ways:
e
e
Light Flashing
-
A misfire condition has been
detected. A misfire increases vehicle emissions
and may damage the emission control system on
your vehicle. Dealer or qualified service center
diagnosis and service may be required.
Light On Steady
-
An emission control system
malfunction has been detected on your vehicle.
Dealer or qualified service center diagnosis
and service may be required.
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