The astronauts only had about an hour and a half left in the spacewalk when mission control noticed the sensor in astronaut Gregory Chamitoff's spacesuit wasn't working.
The astronauts spent their time outside the space station moving around some experiments and performing maintenance tasks.
On Thursday, the shuttle's astronauts accomplished their main job: installing on the station a $2 billion physics experiment that looks for antimatter and dark matter.
There are three more spacewalks scheduled before Endeavour returns to earth.
After a planned 16-day mission, /*Endeavour*/ is scheduled to land June 1.
NASA is shutting down its shuttle program this summer after 30 years, to focus on interplanetary travel.
The Associated Press contributed to this report.