GMC 2003 DURAMAX, Owner'S Manual

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If the Light Comes On
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 it does not, have it repaired. This light will
also come on if an emission control system malfunction
has been detected on your vehicle. Diagnosis and
service may be required.
You also may be able to correct the emission system
malfunction by considering the following:
Did you just drive through a deep puddle of water?
If so, your electrical system may be wet. The condition
will usually be corrected when the electrical system
dries out. A few driving trips should turn the light off.
Are you low on fuel?
As your engine starts to run out of fuel, your engine
may not run as efficiently as designed since small
amounts of air are sucked into the fuel line. The system
can detect this. Adding fuel should correct this
condition. It will take a few driving trips to turn the
light off.
If none of the above steps have made the light turn off,
your dealer can check the vehicle. Your dealer has
the proper test equipment and diagnostic tools to fix any
mechanical or electrical problems that may have
developed.
Emissions Inspection and Maintenance
Programs
Some state/provincial and local governments have or
may begin programs to inspect the emission control
equipment on your vehicle. Failure to pass this
inspection could prevent you from getting a vehicle
registration.
Here are some things you need to know in order to help
your vehicle pass an inspection:
Your vehicle will not pass this inspection if the Check
Engine light is on or not working properly.
Your vehicle will not pass this inspection if the OBD
(on-board diagnostic) system determines that critical
emission control systems have not been completely
diagnosed by the system. The vehicle would be
considered not ready for inspection. This can happen if
you have recently replaced your battery or if your
battery has run down. The diagnostic system is
designed to evaluate critical emission control systems
during normal driving. This may take several days
of routine driving. If you have done this and your vehicle
still does not pass the inspection for lack of OBD
system readiness, your GM dealer can prepare the
vehicle for inspection.
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