During the main engine ignition sequence, a gold pin used to plug an oxidizer post in the Space Shuttle's number three (right) engine came loose and was violently ejected, striking the engine nozzle's inner surface and tearing open three cooling tubes containing hydrogen. These ruptures resulted in a leak downstream of the main combustion chamber. This anomalous event and the automatic response to the leak by the right engine's controller did not violate any launch commit criteria and liftoff proceeded normally. However, approximately 5 seconds after liftoff, an electrical short disabled the center engine's primary digital control unit, DCU-A, and the right engine's backup unit, DCU-B. The center and right engines continued to operate on their remaining DCUs for the rest of powered flight to orbit. The redundant set of DCUs in each engine controller saved "Columbia" and her crew from potential catastrophe, as shutdown of two engines at that point in the flight would have resulted in a very risky contingency abort with no guarantee of success. The electrical short was later discovered to have been caused by poorly routed wiring, which had rubbed on an exposed screw head. This wiring issue led to a program-wide inspection of the wiring in all orbiters.