sls? and a value as it's for sale

Hi, a lad that works for us has a 2008 57 plate D3, full landrover history, the SLS light is illuminated on the dash, does anybody know or had experiences to know what it is? he says it is to do with raising and lowering the suspension, but it doesn't do like the series 2 and sit on its arse, question is does anyone know what this fault is? the vehicle other than that is all ok, he got it from new and he is going to put it up for sale,

57 plate march 08, 17" alloys, black, 7 seat, towbar, lowish spec no leather! full landrover service history, 60,00 miles??there abouts, very good condition
any more info i can get it for you,