Many times a customer has come to me with a Volkswagen 20 valve 1.8T engine complaining that their cam sensor fault code was on. This engine has twenty valves and only four cylinders so timing is especially important. With five valves per cylinder, there is no room for mistakes. If you are only a little off on the valve timing, the cam sensor fault code will pop up. The customer state that they have checked the timing belt specifications over and over and still this code comes on. The answer is that most of these customers have just had their cylinder heads rebuilt. They have just had a “valve job”. The machine shops that have done this valve job have not set the chain that connects the two cams on the head properly. This chain and the two cams must be exactly on the timing marks. Most machine shops are unable to set the cams timing properly. So consequently, no matter how perfectly the timing belt is set,  the cam sensor fault code will pop up. The moral of the story is be careful when you go to get a valve job with a multi valvehead. MAX