I had a CAS issue once, and I was successfully able to repair it.
Take it off the car(mark where it goes), and then when its out mark where the moving parts that interface with the intake cam go so you can put it back correctly.
Then, with some needle nose vice grips or something similar, unscrew the cover. The screws are one way only by design, but you can get them out.
Then look inside, you will see an optical switch. There is a ring with square holes in it, and a small part with a wee little lense. The lense sends light out and when its blocked by the metal ring, it can't get that signal thru. When its not blocked(a hole is there), the light beam can get back across to the other side of the sensor.
Mine was just dirty and cruddy. I cleaned it with brake cleans, a toothbrush and some care. Then I put it back togeather. All has been well for about 5 years now.
Its definately worth a try, as if you are going to swap it you have to pull it anyways.
Oh, put the engine to TDC, then the marks on the CAS(internally) will already be lined up and you won't have to make new ones.
