GMC 1995 Jimmy Owner's Manual page 124

Malfunction Indicator Lamp (SERVICE ENGINE SOON
Light)
b
A
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The amber
SERVICE
ENGINE
SOON
Malfunction Indicator
Lamp (SERVICE
ENGINE SOON
Light) is located at the
top of your instrument
panel.
computer monitors operation of your fuel, ignition and emi ssion control
systems. This light should come on when the ignition is on, but the engine is
not running, as a check to show you it is working. If it does not come on at
all, have it fixed right away. If it stays on, or it comes on while you are
driving, the computer is indicating that you have a problem. You should
take your vehicle in for service soon.
NOTICE:
If you keep driving your vehicle with this light on, after awhile
the emission controls won't work as well, your fuel economy
won't be as good and your engine may not run as smoothly. This
could lead to costly repairs not covered by your warranty.
If Your Vehicle is Equipped with OBD I!
Certain vehicles are equipped with a new emission diagnostic system. You
can tell whether your vehicle has this system by reading your tune-up label
located under the hood. If the label says "OBD 11" on it, the following
instructions apply.
Malfunction Indicator Lamp (SERVICE ENGINE SOON Light)
Your vehicle is equipped with an onboard computer which monitors
operation of the emission control system. This system is called OBD I1
(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'' light
comes on to indicate when service is required. Malfunctions often will be
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