• Code: 7200
• Description: Broken inner thermistor wire (Developer) The sensor input sampling value is greater than the reference value. (After detection, controlled at 25 °C/77.0 °F)
• Remedy: Developer unit BK 1. Confirm that the connector of the developer unit BK is firmly connected, and if necessary, push the unit all the way in. Toner sensor BK - Unit relay PWB (YC9) Unit relay PWB - Main/Engine PWB(YC7) 2. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 3. Replace the developer unit BK.
  Unit relay PWB Replace the unit relay PWB.
  Main/Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the main/engine PWB.

• Code: 7210
• Description: Short-circuited inner thermistor (Developer) The sensor input sampling value is less than the reference value. (After detection, controlled at 25 °C/77.0 °F)
• Remedy: Developer unit BK 1. Confirm that the connector of the developer unit BK is firmly connected, and if necessary, push the unit all the way in. Toner sensor BK - Unit relay PWB (YC9) Unit relay PWB - Main/Engine PWB(YC7) 2. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 3. Replace the developer unit BK.
  Unit relay PWB Replace the unit relay PWB.
  Main/Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the main/engine PWB.

• Code: 7221
• Description: Broken inner thermistor wire (LSU) The sensor input sampling value is greater than the reference value. (After detection, controlled at 25 °C/77.0 °F)
• Remedy: Laser scanner unit (LSU) 1. Confirm that the wiring connector of the LSU is firmly connected, and if necessary, connect the connector all the way in. LSU - Main/Engine PWB (YC21) 2. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 3. Replace the LSU.
  Main/Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the main/engine PWB.

• Code: 7231
• Description: Short-circuited inner thermistor (LSU) The sensor input sampling value is less than the reference value. (After detection, controlled at 25 °C/77.0 °F)
• Remedy: Laser scanner unit (LSU) 1. Confirm that the wiring connector of the LSU is firmly connected, and if necessary, connect the connector all the way in. LSU - Main/Engine PWB (YC21) 2. If the wire is disconnected, short-circuited or has a ground fault, or the connector pin is deformed, replace the wire. 3. Replace the LSU.
  Main/Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the main/engine PWB.

• Code: 7401
• Description: Developer unit type Mismatch error (K) Improper adaptation of the main unit and developer unit is detected.
• Remedy: Developer unit 1. Check if the developer unit of different models is mounted, and replace it to the correct one. 2. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Developer unit - Unit relay PWB Unit relay PWB - Main/Engine PWB(YC7) 3. If the wiring is disconnected, short-circuited or has a ground fault, replace the wire.
  Unit relay PWB Replace the unit relay PWB.
  Main/Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the main/engine PWB.

• Code: 7402
• Description: Developer unit type Mismatch error (C) Improper adaptation of the main unit and developer unit is detected.
• Remedy: Developer unit 1. Check if the developer unit of different models is mounted, and replace it to the correct one. 2. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Developer unit - Unit relay PWB Unit relay PWB - Main/Engine PWB(YC7) 3. If the wiring is disconnected, short-circuited or has a ground fault, replace the wire.
  Unit relay PWB Replace the unit relay PWB.
  Main/Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the main/engine PWB.

• Code: 7403
• Description: Developer unit type Mismatch error (M) Improper adaptation of the main unit and developer unit is detected.
• Remedy: Developer unit 1. Check if the developer unit of different models is mounted, and replace it to the correct one. 2. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Developer unit - Unit relay PWB Unit relay PWB - Main/Engine PWB(YC7) 3. If the wiring is disconnected, short-circuited or has a ground fault, replace the wire.
  Unit relay PWB Replace the unit relay PWB.
  Main/Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the main/engine PWB.

• Code: 7404
• Description: Developer unit type mismatch error (Yellow) Improper adaptation of the main unit and developer unit is detected.
• Remedy: Developer unit 1. Check if the developer unit of different models is mounted, and replace it to the correct one. 2. Confirm that the wiring connector is firmly connected, and if necessary, connect the connector all the way in. Developer unit - Unit relay PWB Unit relay PWB - Main/Engine PWB(YC7) 3. If the wiring is disconnected, short-circuited or has a ground fault, replace the wire.
  Unit relay PWB Replace the unit relay PWB.
  Main/Engine PWB 1. Check the engine firmware and upgrade to the latest version if necessary. 2. Replace the main/engine PWB.