Hi Valk,

The purpose of the crankshaft position sensor is to let the ECU know exactly what the position of the crankshaft is.

On the end of a crankshaft, there are a number of "teeth", otherwise known as a reluctor ring. As the crankshaft spins, the teeth of the ring trigger the crankshaft position sensor, and this lets the ECU know how fast the engine is spinning (RPM). Also, on some reluctor rings, there might be one or several gaps where a couple of the teeth are missing. THe purpose of this gap is to let the ECU know when the #1 cylinder is at TDC (Top Dead Center). This is typically done for engines that don't also have a camshaft position sensor, which isn't the case for the Crossfire engine.

In the Crossfire's case, the reluctor ring on the Crankshaft is solid, and tells the ECU that the crankshaft is spinning, and what the exact RPM of the crankshaft is. The ECU then looks at the Camshaft position sensor to know exactly which cylinder needs to have fuel injected into it, and which spark plugs to fire.

As you can see, without both sensors installed and working perfectly, the ECU will not be able to properly run the engine, as it would only have half of the information that it needs.

As for is any other cars use these sensors, the answer is Yes.
Just about every fuel injected engine must have one of these two sensors.
Typically, cheaper cars use the combination crankshaft/camshaft position sensor that I had mentioned at the beginning.

One of my previous cars, a '92 Buick Park Avenue Ultra, with its Supercharged engine, has both the camshaft and crankshaft position sensors, but, if the camshaft position sensor fails, then the ECU runs a backup program using just the information from the Crankshaft position sensor in order to know what cylinder is at TDC, and which spark plugs need to be fired. When this occurs, the CEL is lit on the dash letting you know something's wrong, and needs to be checked.

I ran my Buick like this for several years, as the cause of the issue was the magnet on the end of the camshaft had fallen off (common problem for that engine), and it was way too expensive for me to have the engine torn apart to replace a magnet, when the car still ran perfectly fine without it.

It actually surprises me that the Crossfire engine doesn't have similar logic in its ECU in order to keep the engine running in the event of a Camshaft position sensor failure.

I hope this helps explain the functionality and the need for the crankshaft position sensors.

BC.