Danielsson's career started in karting in 1998, where he stayed until 1999 before moving up to Formula Ford. In 2004 Danielsson progressed to Formula Renault V6 in Europe and Asia before moving onto the World Series by Renault in Europe.
In 2006 he was racing in the World Series by Renault for the British team Comtec Racing and doing exceptionally well. After suffering two hard crashes that could have ended his season at the Spa circuit in Belgium, he managed to take a double win at Donington on September 9 and 10 2006. He was then able to follow up the victories with a third straight victory at Le Mans on September 30 and a fourth victory in Barcelona on October 28. The following day he clinched the World Series title via a fifth place in the last race of the season.