To find the Cable Guy’s Van Keys in Dead Island 2, you must first find the Cable Guy! Travel to Alpine Dr near Curtis’ house at night during the O Michael, Where Art Thou? story quest to find the Cable Guy.
Defeat him so he’ll drop his keys. The Cable Guy’s van can be found further south on Alpine Dr near the entrance to the Goat Pen. Open the Cable Van Trunk using the Cable Guy’s Van Keys to receive the Electrocutor Tire Iron.