Though his lawyer argues that a "vehicular malfunction" caused the crash that killed a pregnant woman on a midtown sidewalk in March, the van's driver admitted to police that he was drinking before the horrible accident. Keston Brown, 28, first told cops he'd only consumed two Bud Lights before getting behind the wheel, but six hours later he admitted to imbibing more than double that amount at an Upper West Side bar: "We stayed 30 to 40 minutes. I had about three or four bottles of Bud Light and one shot of Hennessey." But Brown maintains that he wasn't drunk, and that the van mysteriously "turned off" before he careened onto the sidewalk and killed Ysemny Ramos, who was two months pregnant. Police sources say that moments before the crash, Brown and his coworker in the passenger seat had been driving alongside Ramos and her friend, "shouting come-ons at the two women from his window before losing control of the delivery van." Yesterday Brown pleaded not guilty to vehicular homicide, manslaughter and assault charges, but a Supreme Court judge refused to lower his bail.