A depleted memory backup battery is a common hidden cause of startup problems, especially in machines that have been idle for a long time. A dead battery will cause the controller to lose its SRAM contents, including system parameters essential for booting. Check the battery voltage with a multimeter and replace it if necessary.
The system initializes the basic input/output system.
Turn on the CNC control power while keeping the keys held down.
In the Boot Screen menu, use the arrow keys to navigate to . Select SRAM CLEAR or ALL SRAM CLEAR . Confirm the action. fanuc starting system software please wait
Ensure the cooling fans on the CNC control unit are functioning and that the cabinet filters are clean. Excessive heat accelerates the degradation of Flash ROM chips and microprocessors.
Re-initializes the software to factory defaults. Use this only as a last resort if you have no backup. Wipes all programs, mastering, and PLC data. Image Restore
If the power supply is failing, the CPU may power up enough to display a message but not enough to read the memory. A depleted memory backup battery is a common
To fix this issue, you must understand what happens behind the screen during startup. When you turn on a FANUC control (such as the 16i, 18i, 21i, 0i-D, or 0i-F series), the system executes a specific boot sequence:
Use a multimeter to check the test points on the FANUC power supply module. If the voltages fluctuate or drop when the screen attempts to load, the PSU needs to be rebuilt or replaced. 📋 How to Prevent Future Boot Failures
If "Please Wait" appears after a normal shutdown and never progresses, do not repeatedly power cycle. This can corrupt the FROM (flash memory). Use IPL mode first. Always maintain current backups – FANUC systems are robust but unforgiving of lost parameter files. The system initializes the basic input/output system
If you reach the "Configuration Menu," select . This bypasses some normal startup checks and may allow you to perform backups or diagnostics. Boot Monitor Mode (BMON)
Disclaimer: The information provided in this article is for general informational purposes only and does not constitute professional or technical advice. FANUC hardware and software systems are complex. You should not rely solely on this information to address a problem with your equipment. Always consult a qualified FANUC service technician and refer to the official FANUC documentation for your specific system model before performing any diagnostic or repair procedure.
