LEXMARK x5150 My printer is reading cartidge error 50c consult users guide the only thing is i can't find it. Could you help me please?

I have one of these and it has had similar problems, errors not listed in the manual. I don't use mine much, so I took out the cartridges and cleaned them as well as the contacts and other surfaces. It didn't help. I replaced the black one and it works now. Your printer cartridges only last so long, even if you don't use them they expire and won't work. Once you remove the cellophane covering, they don't have a long life. Your printer will work without the color cartridge by the way. When the "no color cartridge" error appears, just click continue and it will print in black and white. Don't know if this helps, since your post is older, but I hope it does!!