We can not clear the paper jam error. We have cleared the paper jam, turned the unit on and off, unplugged the unit, moved all the rollers, can not see any pieces of paper that are still in the misfeed but can not clear the paper jam error.

Here's how you can troubleshoot and resolve the problem:

1. Turn Off the Printer: Start by turning off the printer and unplugging it from the power source. This will prevent any further damage and ensure your safety during the troubleshooting process.
2. Open the Printer Covers: Carefully open all the printer covers, including the front cover, rear cover, and any other access points to the fuser unit.
3. Check for Jammed Paper: Inspect the fuser unit and its surrounding areas for any jammed or crumpled paper. Carefully remove any paper you find, making sure not to tear it, as torn pieces can be more challenging to remove.
4. Clear Paper Path: Check the entire paper path, including the input trays, output trays, and any other areas, for any residual paper or debris. Clear any obstructions you find.
5. Check Fuser Unit: Inspect the fuser unit itself for any damage or foreign objects that may be causing the jam. Make sure the fuser rollers are clean and not worn out.
6. Test Printer: After clearing any paper jams and ensuring the fuser unit is in good condition, close all printer covers securely. Plug the printer back into the power source and turn it on. Run a test print to see if the error has been resolved.
7. Reset Printer (if necessary): If the error persists, try resetting the printer. Refer to the printer's user manual or Xerox's support documentation for instructions on how to reset the printer.

This is for other printers, but i guess it can be helpful,

please turn off the unit....

unplug the power cable

now remove the cartridge...manually slide the carriage assembly\ printhead back and forth
also clean the rail against which the assembly slides with a tissue ensuring that there is no ink residue on it
clean the golden contacts of the cartridges and the printhead with a cotton swab dipped in little alcohol
Now check the paper feed tray, roller assembly area and the area where the carriage moved for any stuck obstruction like paper, paper clips, pins etc and if found remove it.
once done turn the unit back on and check

You do not say which model printer you have.
However error code 5100 usually comes up after paper jam.
The error indicates 2 possibilities, either their is something stuck or a sensor detecting the paper jam issues is faulty.

1. turn off the unit....unplug the power cable
2. Remove the cartridge...manually slide the carriage assembly\ printhead back and forth.

3. Clean the rail against which the assembly slides with a tissue ensuring that there is no ink residue on it.

4. Clean the gold contacts of the cartridges and the printhead with a cotton swab dipped in little alcohol.

5. Check the paper feed tray, roller assembly area and the area where the carriage moved for any stuck obstruction like paper, paper clips, pins etc and if found remove it.

6. Turn the unit back on and check

7. If error 5100 continues, then an electric sensor that detects paper jams is faulty.

Sensors can be costly to repair/replace and it is often more cost effective to opt in for a new unit.

First, check to make certain there are no small pieces of paper stuck in the gears of the rollers and carriage. You may have to reach in through the paper tray to move the carriage to see both sides. To do this, the printer must be unplugged.

If you are certain you have cleared the jam, I would do a power reset:
With the printer on -
* unplug the power cord from the back of the printer
* unplug the power cord from the wall outlet
* wait at least 15 seconds
* plug the cord back into the wall
* plug the cord back into the back of the printer
* printer should turn on by itself, if not press power button to turn on
* try to print a test page: (With printer on - while holding the power button in, open and close the front cover of the printer 4 times, then release the power button, self-test should print.)

The following link from the HP Support site is a step-by-step guide to removing paper jams. You may want to follow them to ensure you have cleared all the jams and reset the printer correctly.

The HP Product Stops Printing and the Power Light Blinks or Mechanism...

I'm not sure if you tried this, yet, but try the following link from canonusa.com website regarding clearing paper jams. Click on 'clearing paper jams inside the printer' on the page:

http://www.usa.canon.com/cusa/support/consumer/printers_multifunction/pixma_mp_series/pixma_mp810#ServiceAndSupport

HP Officejet 7200, 7300, and 7400 Series - 'Paper Jam: Clear jam, and then press Enter' Message Displays on the Control Panel Display
Issue
During printing, the paper becomes stuck in the all-in-one and the error message 'Paper Jam: Clear jam, and then press Enter' displays on the control panel display.
Solution
Use the following instructions to clear a paper jam from the product:
Step one: Check for and remove any loose paper from the In tray
Do not try to remove jammed paper from the In tray. First remove any loose paper from the In tray to avoid worsening the jam.
CAUTION: Always try to remove jammed paper from the back of the printer first to avoid mechanical damage.
Step two: Clear the jam from the back of the printer
Follow these instructions to clear jammed paper from the back of the product. If the product is equipped with a two-sided printing accessory, skip to that section.
Remove the rear access door to clear the paper jam

1. Remove the rear access door by pressing the buttons on the side of the door and pulling it toward you.
Figure 1: Removing the rear access door
Rear access door
2. Gently pull the jammed paper out of the rollers.
WARNING: If the paper tears while removing it from the rollers, check the rollers and wheels for torn pieces of paper that might remain inside the product. If all the pieces of paper are not removed from the product, more paper jams might occur.
3. Replace the rear access door. Gently push the door into the all-in-one until it snaps firmly into place.

Remove the two-sided printing accessory to clear the paper jam

1. Remove the two-sided printing accessory by pressing in the buttons on the sides and then pulling the accessory toward you.
Figure 2: Removing the two-sided printing accessory
2. Gently remove any jammed paper.
WARNING: If the paper tears while removing it from the rollers, check the rollers and wheels for torn pieces of paper that might remain inside the accessory. If all the pieces of paper are not removed from the accessory, more paper jams might occur.
3. Press the button on top of the two-sided printing accessory to open the door.
Figure 3: Opening the two-sided printing accessory door
4. Gently pull the jammed paper out of the rollers.
5. Close the accessory door.
6. Reinstall the two-sided printing accessory.

Step three: Clear the jam from the automatic document feeder (ADF)

1. Remove the document feeder tray from the product by gently pulling it.
2. Lift the cover of the automatic document feeder by pulling it outward.
Figure 4: Lifting the cover of the automatic document feeder
Automatic document feeder (ADF) door
3. Gently pull the jammed paper out of the rollers.
WARNING: In the rare occurrence of a severe paper jam, you might need to remove the face plate from the front of the automatic document feeder and lift the pick assembly to remove torn pieces of paper from deep inside the automatic document feeder.
4. Close the cover of the automatic document feeder, and then reattach the document feeder tray.

Step four: Verify that the print carriage can move freely
Follow these steps to try to move the print carriage.
CAUTION: Do not force the print carriage to move if it is out of plain view or feels stuck. Forcing it may damage the printer.

1. With the product turned on, open the print cartridge access door. The print carriage might try to move into the access area. If so, allow it to move to that position.
2. Without turning off the product, unplug the power cord from the back of the product. Unplug the power cord from the power source. The power cord must be unplugged to allow the parts to be moved by hand and to reset the paper feed mechanism, without the risk of an electrical shock.
3. Looking in through either the print cartridge access door or the output paper tray, make sure the print cartridges are locked into the carriage and have not come loose. Also, make sure that there are no obstructions under or around the carriage to block it from moving.
4. Make sure the print carriage can move freely across the width of the product by gently pushing the carriage to the left and then to the right. Clear any obstructions found.
You may have to reach through the output paper tray to access the print carriage.
5. Close the print cartridge access door and plug the power cord back to the back of the product. Plug the power cord into the power source.
6. Press the On button to turn on the product.

Step five: Reload and test the printer
After you have removed the jammed paper, make sure the product is still functioning properly.

1. Reload the product with plain paper.
2. Peform a self-test by pressing and holding the RESUME button on the control panel until the product begins printing. A test page prints.

Step six: Service the printer
If you have completed all the steps listed above and are still experiencing a problem, service the product.

Could there possibly be:

A) Paper jammed internally: Power Off. Open the cover and remove the paper or scrap carefully. Do not touch the internal printer parts. Close the cover. Power on.

B) Foreign objects in printer: Power Off. Open the paper support and confirm that there is no foreign material in the auto sheet feeder. (If so, remove it by hand or with tweezers). Open the front cover and confirm that there is no foreign material in the unit. Avoid touching the inner workings of the machine.

C) Reset the printer:

1. Turn the printer off with the Power button

2. Disconnect the data cable from the printer

3. Unplug the printer's power cord for approximately 10 minutes, and then plug it back in. Attach data cable.

4. Turn the printer back on.

If all of these suggestions fail, your iP1600 may require repair service. Please note: With the suggested retail price of $29.99 USD, repair does not seem cost effective - you could just go out and purchase a new printer.

928 - fuser motor lock error

take out fuser and check for paper stuck on roller
make sure roller can move

if roller is stuck or damaged, repalce fuser unit

Look for little pieces of paper that get stuck in the rollers, also verify that the gears and roller didn't get misaligned when you cleared the jam.
Good Luck, 

Fiend your solution direct from hp. Here is your solution...


http://www.hp.com/printer/prob676ijt65/solution
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