Oh boy the code 41. When you first seen it happen, did you happen to be passing someone or in the higher RPM range??
That is what happened to mine. Basically, one of the things that can happen, is that the end of the camshaft, has a spring and a "button" that sits against the timing chain cover. With time and age, the spring gets weak, and at higher RPM the cam can actually start to "walk" out and the magnet then hits the cam sensor, and you usually have to get the sensor and magnet changed.
You can do it yourself. Try using the search function for "code 41" or "cam magnet".
I will see if I can find the posts that dealt with it.
EDIT: here this is padgett'* webpage with how to do this.