HP LaserJet Pro M16a

MFP M28-M31 only: A blank control panel display (or if the control-panel LED does not illuminate) can be caused by one or more of the following:

• No power to the printer.
• Power supply has tripped (over-current/over-voltage/temperature issue).
• Formatter not fully seated.
• Faulty component installed on the formatter (for example a WiFi PCA).
• Control panel connector not fully seated.
• Faulty formatter.
• Faulty DC controller (on the engine controller unit).
• Faulty control panel.

Troubleshooting a blank control panel (MFP M28-M31 only)

1. Verify that power is available to the printer. If the printer is plugged into a surge protector or uninterruptible power supply (UPS), remove it, and then plug the printer directly into a known operating wall receptacle (make sure that the wall receptacle provides the correct voltage and current for the printer).
2. Make sure that the power switch is in the on position.
3. Make sure that the motor runs briefly (at start up), which indicates that the power supply is operational.
4. Make sure that the control-panel display flat cable is connected.
5. Make sure that the formatter is operating correctly. Turn off the printer and remove the formatter. Reinstall the formatter, make sure the power switch is in the on position.
6. If the control panel display is blank, but the motor runs briefly after the printer power is turned on, try printing an engine-test page to determine whether the problem is with the control-panel display, formatter, or other printer assemblies.
   • With the printer on and in the Ready state, open and then close the cartridge door four times within 5 seconds. The printer prints one simplex engine test page.
   If the engine test page prints, the print engine is operating normally (a failed engine test print page does not necessarily indicate that the ECU is defective).
7. If the print engine appears to be correctly operating (the engine test page successfully printed) and the control panel is still blank (MFP M28-M31 only), replace the ECU.
   NOTE: If the error persists after replacing these assemblies, escalate the problem to the Global Business Unit (GBU).