One problem related to emission control has been reported for the 2002 GMC Sierra 2500. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2002 GMC Sierra 2500 based on all problems reported for the 2002 Sierra 2500.
The truck has several broken exhaust manifold studs that are completely rusted out causing failure of correct emission controls through the catalytic converter, and out of the headers instead. This is environmentally unfriendly, and is really annoying as the exhaust leaks from under the hood due to lack of bolts on the exhaust manifold.