Crankshaft circuit fault means you have either a problem with Crankshaft Position Sensor or it's wiring, before changing it open the sensor wiring connector and clean it from any dust or oil, then check the wiring and make sure you don't have any cracks or anything on the wire, BUT if you have any still existing problem with that sensor your car's engine will not start, and if your car is running now, then it means an error happened on that circuit and it's stored on your car's computer. which you can safely reset the memory and get rid of that code (after a check up of the sensor's wiring and connector). Have a look at it and let me know if you need more advice. Best