Now passing the T-minus 1 hour mark in the countdown. Two scheduled holds are planned at T-minus 20 minutes and T-minus 9 minutes, leading to the target liftoff time of 11:15 a.m., if the hydrogen fuel sensor issue is deemed not a violation of NASA rules.
The Spaceflight Now Launch Blog noted earlier this morning that "as long as the three hydrogen sensors that worked normally yesterday remain good today, NASA will meet its rules governing the hardware and expect to press forward with 3-of-4 sensors for liftoff at 11:15 a.m." Apparently when they detanked yesterday, the bad sensor still tested wet (and probably this morning as well). These sensors are very important and were used for protective action on STS-51F (where the orbiter had a main engine failure due to a high temperature sensor failure) and STS-93 (where a hydrogen leak caused premature fuel expenditure).