DETROIT—General Motors is recalling more than 331,000 diesel pickup trucks in the United States for a second time because the engine block heater cords can short circuit and cause fires. The recall covers certain 2017 through 2019 Chevrolet Silverado and GMC Sierra 2500 and 3500 pickups with 6.6-liter diesel engines and optional engine block heaters. GM says in documents posted Thursday by U.S. safety regulators that shorts can develop in the heater cord or terminals that connect the cable to the block heater. Coolant can leak from the block heater and come in contact with the cable terminals, possibly causing a fire. The heaters are used to keep the block warm in extreme cold temperatures. GM says it has reports of 24 fires potentially caused by the problem from Dec. 3, 2019 through May 28, 2021. The company says it’s not aware of any injuries. Those vehicles were fixed in …