Litmmpro

Hi new to the site, got a question I had issues with my Electric Brake Control module at the back above the spare tire it was corroded causing error, also corroded a wire going into the connector, its ridiculous what GM wants for the wired pigtail for the connector it almost the same price as a whole new aftermarket brake controller so just curious how the after market brake controllers work it doesn't need that module correct? It acts as it owns module runs direct too the 7 pin? Just curious how that works?