One problem related to gas recirculation valve (egr valve) has been reported for the 2002 Chevrolet Trailblazer. The most recently reported issues are listed below.
I own a 2002 Chevrolet Trailblazer LS with approximately 11,000 miles which had an engine failure on thanksgiving 2002. Entering and accelerating to approximately 60 mph on highway in about 25 degree temperature and engine service light appeared followed by reduced engine power light and then engine stopped running and could not be restarted. Dealer advised me that number 4 cyclinder cracked. They further advised me that gm is aware of a manufacturing defect in some Trailblazer engines that was caused by a miscalibration of the machine used to manufacture the engine. Gm replaced my engine at no cost to me under original warranty. This sudden engine failure could have resulted in an accident and possible personal injury if I had not been able to roll the vehicle to the breakdown lane safely. From NHTSA web site.