I have an error code of (E04-02) on a model Workio dp3520

E4-02 is a fuser exit sensor jam. open the left cover (when u face the machine). then there is a metal gate, flip it open, and it will be the sensor in the middle of the path. You can try pressing it to see if it moves freely. You will also need to reset the fuser code
function, original size (ledger), '3' <--press and hold in sequence

then press 9, set, "ram initialize" -> LBP fuser reset, and wait until the left upper corner tells u to reset the power.

The Panasonic web site is, for some reason, particularly devoid of support information for this printer. Unfortunately, you haven't indicated what exactly is occurring when you get this error number, and the site has taken several hours to locate relevant information. Unfortunately, to make a long story short, it appears that service is required, assuming that you have verified all of the obvious general troubleshooting steps (as indicated below).

If you have your manual, that is most often the best place to start to locate the meaning of a particular error. General troubleshooting would lead to suggest that you turn off and remove the power source for several minutes before restarting, see if the machine resets, and if not, follow up as below after checking all obvious error conditions (supplies, communications lines if any, paper jams, etc.) If you do not have your manual, there are a number of manuals relative to this model at:
http://service.us.panasonic.com/operman/findmanual.aspx?model=DP3520. However, the difficulty of locating information at the site would suggest to keep record of this location, as it has taken me nearly 2 hours to find it!

If you look at page 11 of the Copy manual located at http://service.us.panasonic.com/OPERMANPDF/DP3520_COPY.PDF
you will see that it is indicated that, for any error code beginning with E, contact Service.

I have listed below all other such information as I could locate in regard to this printer. However, there is little to no available information regarding operation and/or errors in any of the generally expected and/or accessible areas.

The best bet may be to submit an online request for support directly from Panasonic. Complete the form at http://www.panasonic.com/business/office/support-contact-us-form.asp and they should get back to you. All other references (other than below) refer us to dealers to get support for printers...

I was able to find a contact and number (Paul Wharton 201-392-6561). However, this was on a page re accessibility. Still, it is a Panasonic contact, and hopefully this person could direct you further. Other than that, please see below.

The main pages for this printer are at http://catalog2.panasonic.com/webapp/wcs/stores/servlet/ModelDetail?storeId=11201&catalogId=13051&itemId=66764&catGroupId=13843&surfModel=DP-3520&displayTab=O
AND
http://www.panasonic.com/office/templates/PDIC_HyperDoc.asp?Category=1029&ModelNo=DP-3520

The following is from http://panasonic.co.jp/pcc/products/en/mfp/download/

WORKiO DP-3520, 4520, 6020

• GDI Printer Driver
  Windows 98, Me, NT4.0, 2000, XP, Server 2003, Vista
• PDL Printer Driver
  Windows 98, Me, NT4.0, 2000, XP, Server 2003, Vista
• GDI Printer Driver / PDL Printer Driver
  Windows XP (x64), Server 2003 (x64)
• Adobe PostScript Printer Driver
  Windows 98, Me, NT4.0, 2000, XP, Server 2003, Vista
• Panafax Desktop
  Windows 98, Me, NT4.0, 2000, XP, Server 2003, Vista
• IPX-SPX setup wizard
  Windows 98, Me, NT4.0, 2000, XP, Server 2003