Oldsmobile 2004 Alero - Manual (Page 137)

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 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, transaxle,
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 does not come on, have it
repaired. This light will also come on during a
malfunction in one of two ways:
• Light Flashing — A misfire condition has been
detected. A misfire increases vehicle emissions
and may damage the emission control system on
your vehicle. Diagnosis and service may be
required.
• Light On Steady — An emission control system
malfunction has been detected on your vehicle.
Diagnosis and service may be required.
If the Light Is Flashing
The following may prevent more serious damage to
your vehicle:
• Reducing vehicle speed.
• Avoiding hard accelerations.
• Avoiding steep uphill grades.
• If you are towing a trailer, reduce the amount of
cargo being hauled as soon as it is possible.
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