Devastation Road is a YA mystery by Australian writer Joanna Baker, it’s just been re-released because a sequel coming. It’s a terrific book.
Kerry Greenwood’s Phyrne Fisher series might appeal. There is some sex, but it’s not explicit (more of the, “they went to bed and when they got up in the morning”), sort.
Alan Bradley’s series, which starts with The Sweetness at the Bottom of the Pie, feature an 11 year old sleuth called Flavia. Not YA, but engaging and unusual.
Harlan Cohen, who writes thrillers for adults, has started a YA series, as have Kathy Reichs and John Connolly.
Elizabeth Peters’ Amelia Peabody series and her Vicki Bliss series are excellent fun. Lots of action, very funny and short in both sex and explicit violence.
And while they might seem a bit old-fashioned for a modern teenager, I read Mary Stewart’s romantic suspense books at her age and love them still.