In case anyone has an old Pfaff like the 7570, I found out how to get rid of the error message when you try to sew with no thread in the needle. (like when marking golden threads quilting paper). I googled it and someone had the answer. It's in the manual, believe it or not!
You select the straight stitch, press the info key, press a right arrow key and the error display options pop up on the screen. How long have I had this machine? 10 plus years. Oh well, better late than never. I don't know if the newer Pfaffs work the same way, probably not.
Kathy
PS My Janome 6600 doesn't have such a sensor and doesn't care if I don't have thread in the needle