Where are the cabin air filters on a 2003 GM 2500 pick up truck?
It may or may not be quipped with cabin filters. Go to an auto parts store and ask for a Purolator cabin filter for this vehicle. The filter will come with complete instructions for replacement.
Cabin air filters didn't come until 2000 on the Suburbans. The pickup had them in 1999. The body style change along with features like cabin air filters came first for the pickups in 1999 and then for the Suburbans Yukons etc. . I own a 1999 Suburban 1500 1999 Suburbans DO have a Cabin Air Filter, here is the location: http://www.wixconnect.com/assets/wixcabinairbrochure.pdf