Camshaft Reluctor Wheel
WARNING: This page is about a different car, the 2008 Suzuki Swift +, 2008 Pontiac Wave, and 2008 Chevrolet Aveo. However, it is still accessible from the selected car via links, so may be relevant.
The camshaft reluctor wheel is bolted to the front of the camshaft. The wheel is a smooth track, half of which is of a lower profile than the other half. This track is read in a radial or axial fashion respectively. This allows the camshaft position (CMP) sensor to supply a signal as soon as the key is turned ON, since the CMP sensor reads the track profile, instead of a notch.