Canon i9900 blinking three orange / jam

uninstall it and reinstall it, hopefully it will reset itself then.

I had the same problem with my i9900 - 3 orange flashes on the the error light (Paper Jam) and yet I could slip a sheet of paper in and it would feed through OK. My problem is that the SPRING on the PAPER SENSOR had come off, leaving the sensor in the where it would be if there was a paper jam.

You have to REMOVE the main cover of the printer to find and fix this problem You have to find all of the release points (look for triangles on the plastic covers) where you insert a small tool/screwdriver to (1) press 1 release each side & remove the 2 silver end panels, (2) press 1 release to remove the control switch & carefully disconnect the two connectors inside. Start with the triangle rlease on the lower front left of the main cover, then 1 on the left side, 3 on the back, 1 on the right side, and finally 1 on the lower front right side and gently lift the whole cover off.

You can then look inside with a flashlight from the top rear just behind the left side paper feed roller and see a small switch which pivots when paper is fed through the printer. Feed a sheet of paper and see if the spring is returning it to the normal (no jam) position. I used a long pair of tweezers to reach inside and slip the spring back into its normal position which is behind the small slot on the far right side of the switch. No pictures, but it should be intuitive where the spring should go. Once reinstalled, the switch will move back to the normal position and your paper jam should be fixed.

This SAME MECHANISM is also used in a number of other Canon i & ip series printers so this general approach to fixing this in other models could be the same - (1) remove the cover, (2) locate the switch, and (3) put the spring back into the correct positiion.