The spanner light has multiple functions 1 Service due 2 Oil level 3 DPF blockage ( if there is not a separate DPF light ) If the light is coming back on after being reset either the oil level is over/under filled, the DPF is clogging of the oil sensor is faulty. Check your levels and top up if required, if the level is over full it may suggest the DPF is clogged and the car if failing regenerations and washing the bores with unburnt fuel which is raising the oil level in the sump if this is happening drain and replace the oil & filter and get the DPF regenerated ASAP otherwise engine damage may occur. Also make sure the car has had the correct C2 specification ( low ash ) either 0W30 ( preferred ) or 5W30 oil used, the wrong oil will cause premature DPF clogging.