One committee Democrat, Sen. Tom Carper of Delaware, broke with his side of the aisle and voted "no." A Republican, John Warner of Virginia, voted "yes," allowing the bill to pass.
In December, Environmental Protection Agency Administrator Stephen Johnson turned down California's request for a Clean Air Act waiver that would have allowed the state to require automakers to cut global warming emissions by 30 percent in new cars and light trucks by 2016.
Boxer's bill would deem the waiver approved.
"This bill merely does what the Clean Air Act required to do in the first place," Boxer said.
However, Boxer told reporters that she wouldn't push for full Senate consideration of the legislation because President Bush would veto it anyway. Plus the Senate already has a busy schedule, she said, including planned consideration in June of global warming legislation her committee is writing.
Still, "This shows that the environment committee on a bipartisan vote stood up for the California waiver," Boxer said.
Some senators who voted against the bill, including Carper, cited a new federal law raising fuel efficiency standards, arguing that the California waiver could undercut that measure.
"A national standard makes more sense for vehicles, which, unlike smokestacks, do not stay within one state's jurisdiction," Carper said.
If California had gotten the waiver, other states could have adopted the same controls. Thirteen other states stand ready to -- Arizona, Connecticut, Maine, Maryland, Massachusetts, New Mexico, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington.
Johnson's decision, applauded by the auto industry, has come under fierce criticism from environmentalists and Democrats. Democrats have produced documents indicating Johnson overruled the unanimous recommendation of his career staff and initially favored granting the waiver, before hearing from the White House, which has opposed any mandatory limits on greenhouse gas emissions.