It's pertinent to note that almost all GM vehicles, such as Buick, Pontiac, venture, and trans sport, have got 2 crankshaft position sensors.
1. 24x type, is located behind the crankshaft pulley. Its a hall effect type.The crankshaft pulley has to be removed before getting access to the sensor. This sensor isn't responsible for starting the engine, as is commonly noticed on cars with wholly a single crank sensor like is obtainable on other cars.
The sensor only comes unto play, after the RPM is above 400.
2. 3x, or 7x type sensor. Thus is the sensor directly responsible for the car starting. Its located behind the engine block, and difficult to access. You'll have to jack up the right hand side of the front, and remove that tyre to access it.
Its a reluctor type of sensor, and resembles the the normal configuration of your Toyota or Honda crankshaft position sensor at the pulley.
So, the next time you experience a no start situation, replace the crank position behind the engine block. This should be done, only if the ignition control module has being eliminated as cause if the fault.

Fig1: Ignition control module for a GM trans sport
Fig2: Crankshaft position sensors

PS: sensor at the crank pulley has a bean shaped configuration; while sensor behind the engine block has the normal crankshaft position sensor you might be familiar with.

Hope this post help someone here.