Peugeot's Cyril Despres, who had led overnight, dropped to third place.
"I tried to really focus on the navigation," said Dubai-based Sunderland, who finished the fifth stage with a 12 minute lead over Chilean Pablo Quintanilla.
"There were one or two really tricky places. Sometimes it works out OK and sometimes you have problems. Today it worked out OK for me," added Sunderland, the fifth different motorcycle stage winner in five days.
Bad weather on the first all-Bolivian stage of the event between Tupiza and Oruro meant the day's action was shortened to 219km from 447km.
Quintanilla and early leader Joan Barreda, who was hit with a one-hour penalty on Thursday for refuelling in an unauthorised area, lost their way in the dunes after 150km of the special stage.
The Dakar, one of the world's toughest endurance challenges which ends in Buenos Aires on Jan. 14 after stages in Paraguay and Bolivia, saw another retirement before the stage started with former winner Carlos Sainz pulling out.
Spain's twice world rally champion, whose son and namesake races in Formula One, had rolled his Peugeot into a ravine on Thursday and the car was too badly damaged to be repaired in the time available.
The Dakar Rally started out as a gruelling race from Paris across the Sahara to the Senegalese capital but switched to South America in 2009 for security reasons.
(Reporting by Alan Baldwin, editing by Peter Rutherford)
