Service Manual
Page 43
... sensor SR21 Tray 1 paper sensor SR22 Duplexer refeed sensor (HP LaserJet Enterprise 500 color M551dn and HP LaserJet Enterprise 500 color M551xh only) OHT sensor (in) OHT sensor (out) RD sensor (front) RD sensor (rear) Environmental sensor (temperature and humidity) Yellow toner-level sensor Magenta toner-level sensor Cyan toner-level sensor Black toner-level sensor Toner collection-box-full sensor Motors and fans ENWW Engine...
... sensor SR21 Tray 1 paper sensor SR22 Duplexer refeed sensor (HP LaserJet Enterprise 500 color M551dn and HP LaserJet Enterprise 500 color M551xh only) OHT sensor (in) OHT sensor (out) RD sensor (front) RD sensor (rear) Environmental sensor (temperature and humidity) Yellow toner-level sensor Magenta toner-level sensor Cyan toner-level sensor Black toner-level sensor Toner collection-box-full sensor Motors and fans ENWW Engine...