The led/sw on the car only gets you to the DM module for existing codes that effect emmissions. The real fault codes are in the Engine Management modules, which can be tapped into with a home-made tool at the other pins.
These codes are system specific and give the Tech a better insight to operating systems faults. The Ignition module is at pin #8, so that is where I would want to find out what has been stored there . By the time that info gets to the DM and Check Engine light, you only know there is a problem coming from the Ignition module, but you don't know what specifically made the module send info to trigger a CE lamp at the DM...so you go to that module and see what that one says.
The only time a CE lamp comes on is when the fault gets to the point of effecting emmissions. The individual modules will pick up the fault way before the CE/lamp DM does. It is the ignition module that has sent the DM info that it has detected a fault in the cam sensor circuit that will effect emmissions. So, the ignition module may have more specific stored code info for you. [ at pin#8...tool will get you into that modules fault bank.]