• Code: 7810
• Description: Short-circuited outer thermistor The sensor input sampling valu is less than the reference value. (After detection, controlled at 25 °C/77.0 °F)
• Remedy: Temperature and humidity sensor 1. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Temperature and humidity sensor - Engine PWB(YC10): 30 ppm model - Engine PWB(YC17): 35/40 ppm models 2. If the wiring is disconnected, short-circuited or has a ground fault, replace the wire. 3. Replace the temperature sensor PWB.
  Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the engine PWB.

• Code: 7901
• Description: Drum unit EEPROM error (Black) No response is issued from the device in reading/ writing for 5 ms or more and this problem is repeated 5 times successively. Mismatch of reading data from two locations occurs 8 times successively. Mismatch between writing data and reading data occurs 8 times successively.
• Remedy: Drum unit 1. Unplug the power cord from the wall outlet, and wait five seconds. Then plug in the power cord and then turn on the power switch. 2. Confirm that the connector of the drum unit is firmly connected, and if necessary, push the unit all the way in. 3. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Drum unit - Drum/Developer relay PWB Drum/Developer relay PWB - Engine PWB(YC6) 4. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 5. Replace the drum unit.
  Drum/developer relay PWB Replace the drum/developer relay PWB
  Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the engine PWB.

• Code: 7902
• Description: Drum unit EEPROM error (Cyan) No response is issued from the device in reading/ writing for 5 ms or more and this problem is repeated 5 times successively. Mismatch of reading data from two locations occurs 8 times successively. Mismatch between writing data and reading data occurs 8 times successively.
• Remedy: Drum unit 1. Unplug the power cord from the wall outlet, and wait five seconds. Then plug in the power cord and then turn on the power switch. 2. Confirm that the connector of the drum unit is firmly connected, and if necessary, push the unit all the way in. 3. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Drum unit - Drum/Developer relay PWB Drum/Developer relay PWB - Engine PWB(YC6) 4. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 5. Replace the drum unit.
  Drum/developer relay PWB Replace the drum/developer relay PWB
  Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the engine PWB.

• Code: 7903
• Description: Drum unit EEPROM error (Magenta) No response is issued from the device in reading/ writing for 5 ms or more and this problem is repeated 5 times successively. Mismatch of reading data from two locations occurs 8 times successively. Mismatch between writing data and reading data occurs 8 times successively.
• Remedy: Drum unit 1. Unplug the power cord from the wall outlet, and wait five seconds. Then plug in the power cord and then turn on the power switch. 2. Confirm that the connector of the drum unit is firmly connected, and if necessary, push the unit all the way in. 3. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Drum unit - Drum/Developer relay PWB Drum/Developer relay PWB - Engine PWB(YC6) 4. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 5. Replace the drum unit.
  Drum/developer relay PWB Replace the drum/developer relay PWB
  Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the engine PWB.

• Code: 7904
• Description: Drum unit EEPROM error (Yellow) No response is issued from the device in reading/ writing for 5 ms or more and this problem is repeated 5 times successively. Mismatch of reading data from two locations occurs 8 times successively. Mismatch between writing data and reading data occurs 8 times successively.
• Remedy: Drum unit 1. Unplug the power cord from the wall outlet, and wait five seconds. Then plug in the power cord and then turn on the power switch. 2. Confirm that the connector of the drum unit is firmly connected, and if necessary, push the unit all the way in. 3. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Drum unit - Drum/Developer relay PWB Drum/Developer relay PWB - Engine PWB(YC6) 4. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 5. Replace the drum unit.
  Drum/developer relay PWB Replace the drum/developer relay PWB
  Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the engine PWB.

• Code: 7911
• Description: Developer unit EEPROM error (Black) No response is issued from the device in reading/ writing for 5 ms or more and this problem is repeated 5 times successively. Mismatch of reading data from two locations occurs 8 times successively. Mismatch between writing data and reading data occurs 8 times successively.
• Remedy: Developer unit 1. Unplug the power cord from the wall outlet, and wait five seconds. Then plug in the power cord and then turn on the power switch. 2. Confirm that the connector of the developer unit is firmly connected, and if necessary, push the unit all the way in. 3. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Developer unit - Drum/Developer relay PWB Drum/Developer relay PWB - Engine PWB(YC6) 4. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 5. Replace the developer unit.
  Drum/developer relay PWB Replace the drum/developer relay PWB
  Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the engine PWB.

• Code: 7912
• Description: Developer unit EEPROM error (Cyan) No response is issued from the device in reading/ writing for 5 ms or more and this problem is repeated 5 times successively. Mismatch of reading data from two locations occurs 8 times successively. Mismatch between writing data and reading data occurs 8 times successively.
• Remedy: Developer unit 1. Unplug the power cord from the wall outlet, and wait five seconds. Then plug in the power cord and then turn on the power switch. 2. Confirm that the connector of the developer unit is firmly connected, and if necessary, push the unit all the way in. 3. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Developer unit - Drum/Developer relay PWB Drum/Developer relay PWB - Engine PWB(YC6) 4. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 5. Replace the developer unit.
  Drum/developer relay PWB Replace the drum/developer relay PWB
  Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the engine PWB.

• Code: 7913
• Description: Developer unit EEPROM error (Magenta) No response is issued from the device in reading/ writing for 5 ms or more and this problem is repeated 5 times successively. Mismatch of reading data from two locations occurs 8 times successively. Mismatch between writing data and reading data occurs 8 times successively.
• Remedy: Developer unit 1. Unplug the power cord from the wall outlet, and wait five seconds. Then plug in the power cord and then turn on the power switch. 2. Confirm that the connector of the developer unit is firmly connected, and if necessary, push the unit all the way in. 3. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Developer unit - Drum/Developer relay PWB Drum/Developer relay PWB - Engine PWB(YC6) 4. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 5. Replace the developer unit.
  Drum/developer relay PWB Replace the drum/developer relay PWB
  Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the engine PWB.