What causes boot failure on device?

A boot failure is when a device is unable to complete the boot process and start up successfully. This can be frustrating for users and troubleshooting the cause can be challenging. In this article, we will explore the various potential causes of boot failure and how to fix them.

Firmware Issues

Problems with the firmware or BIOS can prevent a successful boot. Here are some common firmware-related causes of boot failure:

  • Corrupt BIOS: The BIOS or UEFI firmware may become corrupted or damaged, often due to a failed BIOS update or flash. This renders it unable to properly initialize hardware and boot.
  • BIOS settings reset: Changes to BIOS settings like the boot order, enabled devices, or overclocking can cause boot issues. Resetting BIOS to default can resolve this.
  • Outdated BIOS: An outdated BIOS version may be incompatible with new hardware or fail to support key capabilities needed to boot.

Updating to the latest BIOS/UEFI version from the manufacturer will often fix firmware boot problems. On some devices, the BIOS can be reflashed or reset to factory state to restore functioning.

Bootloader Issues

The bootloader is critical code that loads the operating system kernel and kicks off the boot process. Bootloader issues include:

  • Corrupted bootloader: Like the BIOS, the bootloader code can become damaged and unable to load the OS.
  • Bootloader not found: If the bootloader is deleted, moved, or replaced with the incorrect one for the OS, it will fail.
  • Unsupported OS version: The bootloader may be outdated and not designed to work with the newer OS version installed.

Repairing the bootloader requires restoring, reinstalling, or replacing it with the correct bootloader for the OS. This is done from a recovery partition, installation media, or boot disk.

Operating System Issues

Since the operating system is what ultimately gets loaded and run by the boot process, OS problems are a common cause of failure to boot properly:

  • Corrupted system files: Critical OS files like the kernel, drivers, services, and libraries may become damaged or go missing, preventing startup.
  • Incompatible software: New software or driver installations that don’t play well with the OS version can cause conflicts that impede booting.
  • Failed OS update: Bugs in an OS update or upgrade can sometimes corrupt the installation and cause boot problems.
  • Full hard drive: If the primary hard drive or OS partition is completely full, it may fail to boot properly.

OS boot failures typically require repairing or restoring the system files via recovery tools. This may involve startup repair, system restore, or reinstalling the OS if necessary.

Hardware Issues

Since the boot process relies on hardware initialization and detection, hardware problems are a common boot failure culprit:

  • Faulty RAM: Bad memory (RAM) chips can cause random errors and failures to load data properly on boot.
  • Failed hard drive: If the hard drive has bad sectors or mechanical failure, it may not read data to load the OS.
  • Overheating: Excessive heat can cause intermittent failures or crashes during the boot sequence.
  • Loose cables: Check internal power and data cables to ensure all boot devices are properly connected.

Hardware boot problems typically require replacing or repairing the affected components. Possible solutions include replacing bad RAM, swapping failing hard drives, addressing overheating issues, and reseating cables.

Power Issues

Having adequate and stable power is necessary for a successful boot. Power related causes of boot failure include:

  • Dead CMOS battery: The CMOS battery maintains BIOS settings and failure leads to boot issues.
  • Over/under voltage: Out-of-range voltages from the power supply can create stability issues during boot.
  • Power supply failure: A failing or dead power supply can cause intermittent or permanent boot failure.
  • Power button failure: A stuck, broken, or disconnected power button prevents powering on to start boot.

Check power connections and battery voltage. Test or replace the power supply or CMOS battery if faulty. Inspect the power button and connections for any damage.

External Device Interference

Problematic connections and incompatibilities with external devices can also interfere with booting:

  • USB/Thunderbolt devices: Bad USB or Thunderbolt cables or incompatible devices can cause USB-related boot errors.
  • External displays: Booting with non-compatible external monitors or bad video cables can create video initialization issues.
  • Network connections: Bad network cables or configuration problems can sometimes trigger network-related boot failures.

Unplug any unnecessary external devices and try booting without them connected. Update cables, drivers, and firmware for external devices that are needed.

How to Troubleshoot the Cause

When a device fails to boot, there are a number of steps you can take to narrow down the cause:

  1. Examine any error messages during boot for clues about the problem.
  2. Check the BIOS settings and confirm boot order is correctly configured.
  3. Test hardware components like RAM, hard drive, etc. to isolate failures.
  4. Boot from a USB or external drive to see if the main OS is unbootable.
  5. Try booting into Safe Mode, which loads only essential drivers.
  6. Remove unnecessary external devices and peripherals connected to the device.
  7. Research the boot error codes or diagnostic lights appearing on the device.
  8. Reset BIOS/UEFI settings to default and update BIOS/firmware if available.

Target troubleshooting based on when the boot process fails. Problems early in the boot sequence point to hardware or firmware issues, while failure later on typically indicates an OS issue. Try booting from an installation disk or live USB which isolates hardware problems.

Resolving the Issue

Once the cause of the boot failure is determined, you can take steps to get the device booting again:

  • Hardware issue – Replace faulty hardware components or reseat connections.
  • BIOS/firmware problem – Update or reflash the BIOS/firmware.
  • Bootloader problem – Reinstall or replace the bootloader.
  • OS file corruption – Startup repair, system restore, or OS reinstall.
  • Configuration issues – Reset BIOS and confirm settings like boot order.
  • Overheating – Improve ventilation and cooling.
  • Power problems – Replace CMOS battery or power supply.

For hardware repairs, follow manufacturer instructions closely. Backup important data beforehand when making significant software or OS changes.


You can take proactive measures to help avoid boot failures:

  • Keep the BIOS, drivers, OS, and software updated to latest stable versions.
  • Use reputable hardware brands known for reliability and compatibility.
  • Ensure proper ventilation and cooling to prevent overheating.
  • Connect devices to protected power source to avoid electrical damage.
  • Carefully follow instructions when flashing BIOS or performing OS upgrades.
  • Back up critical data in case corruption requires reinstalling the OS.

While occasional boot failures can happen to any device, following best practices in setup, configuration, and maintenance can maximize uptime.


A failure to successfully boot and load the operating system can stem from diverse causes. The most common include hardware failures, power problems, BIOS/firmware errors, bootloader issues, operating system damage, and interference from external devices. Careful troubleshooting and isolation of the specific point of failure allows the underlying problem to be addressed. Typical solutions involve some combination of replacing or repairing hardware, updating BIOS and firmware, reconfiguring settings, repairing or reinstalling operating systems, and eliminating external interference. With persistence and methodical diagnosis, the vast majority of boot failures can be resolved and return the device to proper working order.