Hp LaserJet Pro 400 paper jam in cartridge area

Here's a video that can help you with paper jams:

Here are the steps to clearing a paper jam:

Chances are you have a paper jam. Remove the toner and open the back door and check for a paper jam. If you had a paper jam previously and had the paper tear on removal, look for small strips etc.

Sound like fuser is bad. If it jams under toner it's probably actually jamming in the fuser location which is right after toner

Is the paper stopping just at the cartridge or is it in the fuser. We have had a few of these fail with bad fusers. The only time we have had a cartridge issue is if the drive shaft on the right side of the cartridge falls off.

There is an access door in the back of the printer. Open the door and you should see jammed paper. If not then you have a faulty sensor or switch.

One of my customers has roughly 100 of these pro 400 in service. Many of the constantly display "Jam in cartridge area" We have found the message is not related to any part of the cartridge area. The exit flag spring in the back of the fuser seems to be lightly wound. Carefully turn the end of the spring that rests on the plastic ( closest to you when looking at it) one full turn over the top of the pivot and re-secure back on the piece of plastic. For safe measure, bend the tip of the spring down the piece of plastic so it won't unwind. Secure the tip with a small amount of glue. We dis this to all of the machines in question and have not had a single problem since

A toner certainly can cause a paper jam. However the jam would be located in the area of the cartridge. Easiest way to check is swap the new with the old or a known good toner and see if the problem follows the toner.
hope this helps

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