When a crankshaft sensor begins to fail you get an intermittent stall and/or no start condition. Mechanics use an oscilloscope to check the operation of the sensor. An easy test when the motor does not start is to test for spark and injector pulse. When they are absent it's usually the crankshaft sensor that's bad. If the special "noid light" is not available you can just listen to hear the clicking noise the injectors make when working.
When the crankshaft position sensor does not work, it can't send TIMED electrical impulses to the ignition coil/s and the motor will not start. They're inexpensive to replace!
There are many. One is the car won't run.
