My wife got me a Canon MX300 printer a while ago in the sales, I maybe used it to print one item before it got plagued by an error message saying that the paper was jammed, even though there was no paper in the machine. I tried everything to try and free the paper jam, but the error wouldn't go away and I couldn't see any kind of debris inside the machine. After a bit of googling, I found that the MX300 is prone to strange paper jams, and so after figuring out what was wrong with my machine, I thought I would post this here so others may find it and hopefully fix it on their end too.

After playing around with flashlights and tweezers and still no look, I decided to just say 'To heck with this' and actually open up the printer, in the event that there might be something covering the sensor that I had missed. Unlikely seeing as it was brand new, but you never know! The printer itself was surprisingly easy to open and get around inside. I have opened & fixed several laser printers before, so I didn't worry about being inexperienced enough to handle this puppy. If you attempt to open your machine, be extremely careful when you take the scanner portion off, as the ribbon cables are rather sensitive and you really don't want to break them!! If you do decide to take apart your machine, you do so at your own risk!!

After a few minutes of pulling stuff apart, I finally got as far into the machine as I could. Out of the corner of my eye, I caught the paper feed sensor in the 'Engaged' position, which tells the printer that a piece of paper is being fed through the machine. Upon further investigation, I found a black wire tie that was blocking the sensor from going back to the OK position. It actually kind-of made sense, as when I got this machine, it was held inside the box by an insane number of these things, and one could very well have fallen inside, or fell in from the factory. After removing the wire and putting the whole thing back together, I powered it on and low and behold, no more paper jam was being reported!

I have posted some pictures of the part in question, for those who might not know where/what to look for. I apologize if the clarity isn't the greatest, but you should at least be able to figure out from here where to find the problem on your machine (if it's the same sensor giving the trouble!). If you found this posting helpful, feel free to leave comments. Thanks!

Here you can see the paper sensor behind the roller wheel. You do have to take off the cover to completely see it, unfortunately.

Here is a much closer image showing the paper level. When the machine is loaded with paper, the lever will be pulled forward, allowing the laser between the two pillars to shine though the whole way. Be sure to clear as much dirt and debris from here as possible. My cable tie was wrapped up around this lever, holding it forward all the time (so it thought that it was loaded with paper).

Here is a distance shot of the printer in it's torn-apart stages, showing you where the sensor is in relation to the rear of the printer. The large black piece sticking up is actually the flat piece of the printers insides; There are several fiddle wires holding this in place, I chose not to disconnect it, but with enough playing around you could probably remove it if you had to.