GMC T-Series 2007 Owner's Manual page 16

Claims Procedure
As with the other warranties covered in the
separate warranty booklet, take your chassis to
any authorized GM dealer facility to obtain service
under the emission warranty. This should be done
as soon as possible after failing an EPA-approved
I/M test or a California smog check test, or at any
time you suspect a defect in a part.
Those repairs qualifying under the warranty will
be performed by any GM dealer at no charge.
Repairs which do not qualify will be charged to
you. You will be notified as to whether or not
the repair qualifies under the warranty within a
reasonable time (not to exceed 30 days after
receipt of the chassis by the dealer, or within
the time period required by local or state law).
The only exceptions would be if you request
or agree to an extension, or if a delay results
from events beyond the control of your dealer
or GM. If you are not so notified, GM will provide
any required repairs at no charge.
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In the event a warranty matter is not handled
to your satisfaction, refer to the "Customer
Satisfaction Procedure" in the warranty booklet
under "Owner Assistance".
For further information or to report violations of the
Emission Control System Warranty, contact the
EPA at:
Manager, Certification and Compliance
Division (6405J)
Warranty Claims
Environmental Protection Agency
Ariel Rios Building
1200 Pennsylvania Avenue, N.W.
Washington, DC 20460
For a chassis subject to the California Exhaust
Emission Standards, contact:
State of California Air Resources Board
Mobile Source Operations Division
P.O. Box 8001
El Monte, CA 91731-2990