Here is the Text of the TSB:

Engine - Serpentine Drive Belt Wear Information

Bulletin No.: 04-06-01-013

Date: April 29, 2004

INFORMATION

Subject:
Information on Serpentine Belt Wear

Models:
2004 and Prior Passenger Cars and Trucks
2003-2004 and Prior HUMMER H2

All current GM vehicles designed and manufactured in North America
were assembled with serpentine belts that are made with an EPDM
material and should last the life of the vehicle. It is extremely rare
to observe any cracks in EPDM belts and it is not expected that they
will require maintenance before 10 years or 240,000 km (150,000 mi) of
use.

Older style belts, which were manufactured with a chloroprene
compound, may exhibit cracks depending on age. However, the onset of
cracking typically signals that the belt is only about halfway through
its usable life.

A good rule of thumb for chloroprene-based belts is that if cracks are
observed 3 mm (1/8 in) apart, ALL AROUND THE BELT, the belt may be
reaching the end of its serviceable life and should be considered a
candidate for changing. Small cracks spaced at greater intervals
should not be considered as indicative that the belt needs changing.

Any belt that exhibits chunking should be replaced.