During space shuttle main engine checkouts, the backup controller for engine 3 did not turn on as expected. There appeared to be an issue with one of three power phases, which was narrowed down to either a cockpit circuit breaker or switch that provides power. The circuit breaker and switch were turned off and on, restoring power.
Engineers continue to analyze data that showed voltage irregularities and will meet this afternoon to review their data. The Mission Management Team now will convene at 5 p.m. EDT to assess the issue.