HP LaserJet printers have the capability of keeping track of the number of pages printed and the remaining toner in the cartridge. The printer will refuse to print if the toner measure falls below a critical level. This measure of the remaining toner is set to signal "Low Ink" messages at a safe margin. However, it may not be accurate at all times. If you physically check the remaining toner inside the cartridge, the cartridge may still have remaining toner. In such a condition, you can perform a cold reset of the printer, which also resets the chip of the toner cartridge tracking the remaining toner. You can then keep printing until you can see a visible faded effect in the printouts, which means that the cartridge is actually short of toner.
Turn off the printer.
Press and hold down the "GO" button.
Turn on the printer with the "GO" button still pressed down. The display of the printer will show a message reading "Cold Reset." If your printer doesn't have a display panel, its attention lights will turn red.
Release the "GO" button. The display will show "Initializing," followed by "Restoring" and "Offline." If your printer is one without a display, its lights will begin cycling from front to back and then stop.
Press the "GO" button again to bring the printer back to online mode.