Dell P1500 Personal Mono Laser Printer - Manual (Page 68)

What this light sequence means:
The printer detects defective flash memory.
What you can do:
Press and release Continue to clear the message and continue
printing. Downloaded fonts and macros not previously stored in flash
memory are deleted.
Refer to the Owner's Manual for instructions to install flash memory.
Secondary error code
What this light sequence means:
The printer detects unformatted flash memory.
What you can do:
Press and release Continue to clear the message and continue
printing. The job may not print correctly.
Reformat the flash memory.
If the error message remains, the flash memory may be defective and
should be replaced.
Secondary error code
What this light sequence means:
The printer has insufficient memory to free up unused space in flash
memory.