General Motors will keep two of its assembly plants shuttered until at least mid-April, another until the end of March and will idle a fourth, all due to a severe shortage of semiconductor chips used in various vehicle parts. But the automaker is doing everything it can to protect the production of its full-size pickups and SUVs, which are its big profit makers. Demand for semiconductor chips is up in part because of the coronavirus pandemic and increased demand for laptop computers and other personal electronics that use the chips. Cars also use them in a variety of parts and infotainment systems. In fact, one car part could use 500 to 1,500 chips depending on the complexity of the part, analysts said.