May be your transfer roller which would sit right under your toner, but before replacing that it could also be a dirty lens on your laser asm. That would be right above your toner.
Fuser warm-up failure
• The thermistor /1 does not detect the specified temperature and the warm-up cycle is not completed even after the lapse of a given period of time after the cycle has been started.
For what color? Replace the image cart associated with color asking for mite have a bad I/c. Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f
Everything you checked sound good. Might be printer software problem, and needs to be re-flashed. Software only available from secure web site that a technician would have, see what it cost if to much buy a new one with extra bells and whistles ! Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f
Modem option is not working. Have a tech look at it. The FAX board might be bad, check you phone line also call ATT. Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f
Ozone Filter Fan is bad or not turning due to DUST or dirt remove all covers and clean all filters and fans Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f