Remedy: Poor contact in the fuser thermistor connector terminals. Reinsert the connector. Broken fuser thermistor wire. Replace the fuser unit. Fuser thermistor installed incorrectly. Replace the fuser unit. Fuser thermal cutout triggered. Replace the fuser unit. Fuser heater lamp installed incorrectly. Replace the fuser unit. Broken fuser heater lamp wire. Replace the fuser unit.
Code: 6400
Description: Zero cross signal error The zero cross signal does not reach the control PWB for specified time.
Causes: Defective harness between high voltage PWB (YC202) and control PWB (YC23), or improper connector insertion. Defective connection between power source PWB (YC103) and high voltage PWB (YC201). Defective power source PWB. Defective control PWB.
Remedy: Defective harness between high voltage PWB (YC202) and control PWB (YC23), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness. Defective connection between power source PWB (YC103) and high voltage PWB (YC201). Reinsert the connector. Defective power source PWB. Replace the power source PWB. Defective control PWB. Replace the control PWB.
Code: 7990
Description: Waste toner full The waste toner sensor has detected that the waste toner reservoir (drum unit) is full.
Causes: Waste toner reservoir (drum unit) is full. Defective waste toner sensor. Defective control PWB.
Remedy: Waste toner reservoir (drum unit) is full. Turn the main power switch off/on to restart the printer. If the error is not resolved, replace the drum unit. Defective waste toner sensor. Replace the waste toner sensor. Defective control PWB. Replace the control PWB.
Code: F000
Description: Control PWB - Operation panel PWB communication error
Causes: Defective harness between operation panel PWB (YC1) and control PWB (YC7), or improper connector insertion. Defective operation panel PWB. Defective control PWB.
Remedy: Defective harness between operation panel PWB (YC1) and control PWB (YC7), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness. Defective operation panel PWB. Replace the operation panel PWB. Defective control PWB. Replace the control PWB.
Code: F020
Description: Control PWB RAM checksum error
Causes: Defective main memory (RAM) on the control PWB. Defective expanded memory (DIMM).
Remedy: Defective main memory (RAM) on the control PWB. Turn the main power switch off/on to restart the printer. If the error is not resolved, replace control PWB. Defective expanded memory (DIMM). Replace the expanded memory (DIMM).