The correct method is the next one:
Press and hold down the  button on the keypad for 4 seconds or longer, and then press (and quickly release) the [Start] button while still keeping the  button pressed.
"_ _ _" is shown on the display.
Use the keypad to enter the 6789
Press the [Start] button.
Once in the Diagnostic Mode, "C_ " (Chain Code input screen) is shown on the display.
Use the keypad to enter the 999
Pressing the [Start] button will show the "L_ " (Function Code input screen) on the display.
Use the keypad to enter the 993
Press the [Start] button again.
While the NVM is being initialized, "run" is displayed.
When NVM initialization is complete, you will be returned to the Function Code input screen.
Switch the machine OFF and then ON again.
here you go :
The SysAdmin Password has been lost or forgottenCause:
To reset the administrator password, power off the machine, remove the NVM Battery on the AIOC PWB for one minute.
Re-install the NVM battery on to the AIOC PWB, then power on the machine.
Note: this will clear all configuration and registration settings, these will need to be reset.
I recently got changed the password and username of a WC 5020DN. But I didnt document the password.
Is there any procedure I can follow to reset password? I didn't find any on the user manual.
I tried to push 0 (5 sec) + start, then 6789
but without success !!
Thanks in advance for your help.