GMC 2003 Sierra - Manual (Page 200)

Madlfiqations to the engine^
transmlssiarr. exhauEl. Intake or fuel system of your
vehfcJe or the repJacemem of the original tires
with other than those of the same Tine Peiiormance
Criteria (^PC) can affect your veh[pie's emiasion
controls and may cause this light to come on.
Modiflcatiorts to iheae ayslems could lead to costly
repairs not covered by your warranty. This may
also result in a failure to pass a rw^uired Emission
Inspectlon/Malntenance test.
This light should come orij as a chack to show you It is
worfting, when ihe igrilion is on and the engine is
not running. If the tight doesn't come on, have It
repalredr This tight witl also come on during a
malfurvctton In one of two ways:
• Light Flashing — A misfire concJHton has been
dataclfid. A misfire increases vehicle emissioris
and may damage the amission control system on
your vehicle rJealer
or qualified service canter
diagnosis and service may be required.
• Light On Steady — An emission control System
ma1furH:iion has been detected on your vehicle.
Dealer or qualified service center diagnosis
and service may be required.
The toliciwing may prevent more serious damage to
your vehicle:
• Reducing vehicle speed
• Avoiding hard acceJerattens.
• Avoiding sfeep uphilt grades.
• If you are towing a iratlein reduce The amount of
cargo being hauled as soon as it Ls possible.
If the iighi stops flashing and remains on steady, see "If
the Light Is On Steady’ following.
If the light continues № ITesh, when it is safe to do so,
stop ihe vehicie. Find a safe place to park your vehicle.
Turn the key off. wait ar feast tO seconds and restart
(he engine. If the light remains on steadyf see "'If
Ihe Light Is On Steady" following, tf the light is still
rfashing, foflow !he previous steps, and drive the vehicle
to your dealer or qualified service center for service.
If the Light is Flashing
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