Your car engine will most likely not run without a crankshaft position sensor. If your car's crankshaft position sensor goes bad, the engine may not start because it won't be able to tell when the spark plugs should fire. However, if your car uses camshaft position sensors, it is possible that the ECM will use these instead of the crankshaft position sensor. So in this case your car could potentially run without the crankshaft position sensor.