Hi Hlounnaci,
The 6004 error can be caused by a paper jam. Please follow all of the steps provided on these 2 pages:
TS6400 series > Paper Is Jammed > Paper is Jammed Inside Printer
TS6400 series > Paper Is Jammed > Removing Jammed Paper from Rear Side
If the 6004 error persists, your TS6420a may require service. If your PIXMA TS6420a was purchased less than a year ago, please contact one of Canon's Technical Support Representatives via phone or chat to obtain your in warranty options. To contact a Technical Support Representative, please use the link below to log into your My Canon account:
https://mycanon.usa.canon.com
Once logged in, click on your PIXMA TS6420a and then click on the Product Support button. When that page loads, click on either the Phone Support button or the Chat Support button to access support.
If your TS6420ais out of warranty, you are eligible for Canon's Upgrade Program. This is for out of warranty units which have been diagnosed to require service, or for some reason are incompatible with a new or upgraded system. This option allows you a one-time opportunity to purchase a replacement product, discounted from the list price.
If you would like to take part in this option, please call our Sales Department at (866) 443-8002 Monday through Saturday, 9am to 9pm. Let them know you have been working with technical support and the Canon Upgrade Program was offered.
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