• Code: U16, U17
• Display: Tray 4 I/F Error U16, Power Off/On Tray 5 I/F Error U17, Power Off/On
• Description: U13-Tray 4 I/F Error U14-Tray 5 I/F Error
• Remedy: 2. Inspect the interface connector connecting the tray unit to the print engine. Inspect the printer’s corresponding connector on the underside of the printer. Inspect the wiring harness leading from the connector to the engine control board. 3. Replace the engine controller board.

• Code: U18, U19,U20, U21
• Display: Un-LED Bar Missing [U18-Yellow LED Bar Missing] [U19-Magenta LED Bar Missing] [U20-Cyan LED Bar Missing] [U21-Black LED Bar Missing]
• Description: The LED bar is either missing or requires reseating to be recognized by the printer. Turn off the printer, wait 15 seconds, then turn on the printer.
• Remedy: 1. Ensure the LED assembly is correctly installed. 2. Inspect the wiring harnesses leading to the LED assembly. 3. Replace the engine controller board.

• Code: U2
• Display: U2-Engine EPROM Error
• Description: During the printer’s self diagnostics there was a problem reading the engine EPROM. Turn off the printer, wait 15 seconds, then turn on the printer.
• Remedy: 1. Turn the printer off and then on 2. Reset the printer NVRAM using the procedure “Resetting NVRAM”. Replace the engine controller board.

• Code: U22, U23, U24, U25
• Display: Un-Toner Missing [U22-Yellow Toner Missing] [U23-Magenta Toner Missing] [U24-Cyan Toner Missing] [U25-Black Toner Missing]
• Description: The toner is either missing or requires reseating to be recognized by the printer. Turn off the printer, wait 15 seconds, then turn on the printer.
• Remedy: 1. Inspect the toner cartridge sensor flag. Ensure to moves properly and is not broken. 2. Test the sensor using the test described in “Switch scan test”. Inspect he toner sensor boards wiring harness. 4. Replace the toner sensor board. 5. Replace the engine control board.

• Code: U26, U27, U28, U29
• Display: Un-Drum Error [U26-Yellow Drum Error] [U27-Magenta Drum Error] [U28-Cyan Drum Error] [U29-Black Drum Error]
• Description: The imaging drum is either missing or requires reseating to be recognized by the printer. Turn off the printer, make sure the imaging drum is properly installed and turn on the printer. If the problem persists, install a new imaging drum.
• Remedy: 1. Remove and install the drum unit. 2. Inspect the spring-loaded drum unit contacts (in a set of three). Ensure they are clean and move up and down freely. Remove the assembly and reseat it, if necessary. 3. Test the drum unit contacts using the Drum contact switch test listed in “Switch scan test”. Install a new drum unit. 5. Replace the engine controller board. 6. Replace the print unit chassis.

• Code: U3
• Display: U3-Engine EPROM Missing
• Description: During the printer’s self diagnostics there was a problem detecting the engine EPROM. Turn off the printer, wait 15 seconds, then turn on the printer.
• Remedy: 1. Turn the printer off and then on 2. Reset the printer NVRAM using the procedure “Resetting NVRAM”. Replace the engine controller board.

• Code: U4
• Display: U4-Engine SRAM Error
• Description: During the printer’s self diagnostics there was a problem reading the engine SRAM. Turn off the printer, wait 15 seconds, then turn on the printer.
• Remedy: 1. Turn the printer off and then on 2. Reset the printer NVRAM using the procedure “Resetting NVRAM”. Replace the engine controller board.

• Code: U5
• Display: U5-Engine Control Error
• Description: During the printer’s self diagnostics there was a problem with the internal control logic. Turn off the printer, wait 15 seconds, then turn on the printer.
• Remedy: 1. Turn the printer off and then on 2. Reset the printer NVRAM using the procedure “Resetting NVRAM”. Replace the engine controller board.