Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
What that red error light means, depend upon which light it is.
If it is the toner light, you have a toner system problem, possibly low toner sensed. (How long ago did you change out the toner, and how many pages have been printed since then? if very high-density or graphics-rich pages, count them as 2 (two) pages each.)
If it is some other light, it means something else... if so, please let me know in Reply To Expert, in order that I may help you further with this case and offer more advice.