Error code 6500 flashing

The 6500 error code is a logic board error code. The PCI Bus error is detected by the ASCI. Sounds like it needs new logic board. but i suggest you to first of all you can try to reset your printer -

1. Turn the printer off with the Power button (if available).
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. 
4. Turn the printer back on. If this works you're done, if not try the next step.

1. After confirming that the printer is powered on, open the paper output tray.
2. Open the top cover and wait until the print head moves to the center.
3. Open the inner cover and check that ink tanks are properly seated.
4. Properly seated
5. Press down on each ink tank until a click is heard.
6. Close the inner cover and top cover

if reset method not works for you then you go for the new logic board replacement .............

Good Luck!!

Thanks