One problem related to front seat power adjust has been reported for the 2015 GMC Sierra 3500. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2015 GMC Sierra 3500 based on all problems reported for the 2015 Sierra 3500.
1st incident veh didn't switch from 4 to 2wd, stop veh, work switch, went to 2wd. Same time driver seat went full forward, seat back full forward, brake pedal full towards driver. Able to readjust, onstar said various electrical - believe modules- problem. Was able to drive, took to dealer, unable to replicate. Few months later adjusted gain on electric trailer brake control - while in motion. Same proplem, seat and seat back full forward, brake pedal full towards driver. Luckily I knew what was happening and wasn't startled. 4wd control @ gain control above each other, left side of dash. No other trbl with veh. A 2015 GMC 3500 crew cab 4wd diesel long box, numerous options including heated-cooled leathe power seats & power adjust pedals. Both pedals moved together towards me. Mileage 1st time, less than 10,000 2nd time less than 13,000.