Canon MP198 Printer Error E3 is becaused something inside of the printer that makes paper sensor not function properly. To fix this error E3 you must open inside of the printer to remove the things.
Look at the paper sensor there is must be somethings in it. I found this when my printer Canon MP198 got error E3. I found small part of paper in the sensor that makes sensor not function properly. I just remove the paper and the printer working again. Enjoy!