GMC Sierra Hitch Wiring | Harnesses, Adapters, Connectors wwwd››Trailer Hitches›Hitch Wiring›GMCWhen your trailer brake lights or turn signals work poorly or don’t operate, make sure your hitch wiring is in good condition. In case it’s faulty and requires replacement, don’t lose your time going from one store to another as you will find a huge range of top-notch GMC Sierra hitch wiring from leading brands here. 2019 GMC Sierra Hitch Wiring | Harnesses, Adapters, Connectors wwwd››Trailer Hitches›Hitch Wiring›GMC›SierraGMC Sierra 2500 HD / 3500 HD With Factory 7-Way 2019, 7-Way U.S. Car End Connector by Reese Towpower®. REESE Towpower 7-Way plug-in adapter for factory-wired vehicles is designed to easily plug a 7-Way connector into a factory equipped..