Black screen after enabling Secure Boot + enrolling Platform Key in BIOS — no POST, no display, CMOS reset didn’t work

Troubleshooting Guide: Resolving Black Screen Issues After Enabling Secure Boot and Platform Key Enrollment on Gigabyte B460M Motherboards

Introduction

Enabling Secure Boot and enrolling Platform Keys (PK) are essential steps for enhancing your system’s security posture. However, these configurations can sometimes lead to unforeseen boot issues, especially if they are not applied correctly or if the system’s firmware enters a restricted state. This article provides a comprehensive troubleshooting approach based on real-world experiences with Gigabyte B460M DS3H AC motherboards, emphasizing potential recovery methods when encountering a black screen post-configuration.

Scenario Overview

A user attempted to enable Secure Boot in BIOS, which required enrolling Platform Keys. After saving changes and rebooting, the system powers on—with fans spinning and peripherals lighting up—yet fails to display any output, never reaching the Power-On Self-Test (POST). Conventional CMOS reset methods proved ineffective, leaving the user concerned that the system might be bricked or stuck in a non-bootable UEFI state.

Key Observations:

• No display output remains even after multiple hardware resets
• Fans and LEDs indicate the system is powered
• Peripherals are active, but no BIOS splash screen appears
• BIOS Flashback or Q-Flash Plus features are unavailable on this motherboard version
• Removing and disconnecting hardware components does not restore video output

Potential Causes

The primary suspect in such scenarios is that enrolling the Platform Key (PK) has inadvertently locked the firmware into a Secure Boot mode that the system cannot initialize properly without a valid EFI environment. Possible contributing factors include:

• Incorrect PK enrollment
• Firmware corruption or misconfiguration
• Hardware incompatibility or faulty hardware components

Troubleshooting and Recovery Strategies

1. Basic Hardware Checks

2. Ensure all hardware components are properly seated.

3. Confirm that primary display outputs (HDMI/DisplayPort) are connected to the onboard GPU or external GPU as applicable.

4. Test with different display cables and monitors to rule out peripheral display issues.

5. CMOS Reset Procedures

Although initial CMOS reset attempts did not resolve the boot issue, it is essential to confirm these steps:

• Remove the CMOS battery and wait at least 10 minutes before reinstalling.
• Use the motherboard jumper (CLR_CMOS) to clear the BIOS settings for 10–15 seconds.

• Disconnect all non-essential peripherals and drives to minimize variables.

• BIOS Recovery Options

Since the motherboard lacks Q-Flash Plus or similar firmware recovery features, options are limited