GMC 2003 Envoy - Manual (Page 166)

Malfunction Indicator Lamp
Service Engine Soon Light in the United
States or Check Engine Light in Canada
United States
Your vehicle is equipped wilh a compuler which
mentters operation of the fuel, ignition and a^niss^on
confrol systems.
This system istaHed OBD II fOn-Board
Diagnostics-Second Generation) and Is intended to
assuiie that emissions are al acceptable levels tor the life
of the vehicle, helping lo pnoduce a cleaner enviromnent.
Ttie SEFtViCE EMGINE SOON or CHECK ENGINE lighl
comes on to indicate that There is a problem and service
Is required. Maltunchons often will be indicated by the
systam betore any problem is apparent. This may prevent
more seriotjs damage to your vehicle. This system is also
destgnod to assist your service technician in correcUy
diagnosing any maliunctfon.
Notfcs: It you Weep driving your vehicle with this
light after a while, your emission rxintrots
may not work as wellt your fuel economy may not
be as good and your engine may no1 run as
fimoDthly. 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 cnutd lead lo costly
repairs not covered by your warranty. This may
also result in a failure to pass a required Emission
lnspection/Mainter>Bnce lest.
З^A^