my service manual says: ( and i can send the service manual if you like- and see the attached PDF)
93:YZ Unable to pressurize the Ink Delivery System.
Try the following:
␣ Switch the Power OFF from the back of the Printer and disconnect the Power cord. Reconnect the power cord and power On the Printer.
␣ Perform the Ink Delivery System diagnostic test to further troubleshoot the problem. ⇒ Page 4-39
␣ If the problem persists, contact HP support.
Service Key Combinations
␣ Diagnostic mode With the printer OFF, press and hold the UP and OK keys. While holding the Up and OK keys down, press and hold the Power key to turn on the printer. Hold all three keys until the Power key stops flashing, usually about 5 seconds.
␣ Service Menu (Service Engineers Only) From the main menu, press and hold the Up and Cancel keys.
␣ Service Menu (For users) From the main menu, press and hold the Down and Cancel keys.