Car quit just driving down road.Starter just clicked. Pulled starter all good, but Crankshaft was locked up. Reversed crank W/Socket & Breaker Bar and it turned over w/starter back in, but won't fire. After turning over locked up again. Same procedure and it unlocks. It's like Timing Chain or Cam locking it up. What would cause this? Crankshaft Sensor? Knock Sensor? Any idea?