This tip can be found many places. I just copied it here for safekeeping
My rather new Brother started raising “false” alerts (at least I think they’re false…) about empty/dead toner, “Toner Life End” it said on the device display. I had only printed a few hundred pages so far. In search for an answer Google directed me to http://www.fixyourownprinter.com/forums/laser/39806.
It’s a long and chaotic thread but about 1/5 from the top there is a posting that advises to do following for Brother HL-4040 and similar models.
How to reset toner warning “Toner Life End”
For the toner life reset menu:
1 Open the front cover of the printer
2 press and hold the cancel button
3 press the reprint button while still holding cancel
– here is the reset menu – go to the appropriate cartridge on
– the menu and reset it and you’re done!
– It seem to work the easiest, if you do it quickly
FYI… Pressing the “Go” button and the up arrow gives you the parts life reset menu (drum, laser, fuser, etc.)
I also did the electric tape over the windows – which worked before the reset – but I thought this fact would be helpful too.
For anyone that is asking “what window?” I think it is the clear plastic opening on the sides of the cartridges where you can actually see the powder inside the cartridge – the color of the toner (magenta, yellow, or cyan). I didn’t really know that for sure when I tried, but it made sense, and it worked. So I am fairly sure that is the “window” you should be trying to cover.
Comment from “Jezza P”
NB – every cartridge is listed twice on the reset menu “-H” for High capacity cartidges and “-S” for standard – make sure you pick the correct one for your cartidges otherwise it errors. 130 are standard and 135 are high.