HP Z2 G8 Workstation does not power off completely unless PCI Express Power Management is enabled

[MRGEOCAD]

Hello everyone,

I am experiencing a very unusual power management issue with my HP Z2 G8 Tower Workstation and I would appreciate any advice or confirmation from HP if this is expected behavior.

System configuration:
- HP Z2 G8 Tower Workstation
- Intel Core i7-11700K
- 32 GB RAM
- NVIDIA RTX A2000 (factory installed)
- Windows 11 Pro 25H2 (Build 26200)
- BIOS Version: T50 01.06.12

Problem:

The workstation does not complete either a normal shutdown or a restart.

Shutdown behavior:
When I select "Shut Down" in Windows, Windows closes normally and the monitor turns off. However:
- the power LED remains ON
- all system fans continue spinning
- the workstation never reaches a complete S5 (soft off) state
- I must hold the power button for about 5 seconds to completely turn it off.

Restart behavior:
When I select "Restart", Windows shuts down correctly, but the system never powers back on. Instead, it remains stuck with the power LED continuously illuminated and the fans running. The workstation never completes the reboot process and requires a forced power-off.

After extensive troubleshooting, I discovered that enabling the following BIOS option completely resolves BOTH issues:

PCI Express Power Management

With this option ENABLED:
- Shutdown works correctly.
- Restart also works correctly and the system powers back on normally every time.

With this option DISABLED:
- The shutdown problem immediately returns.
- The restart problem also immediately returns.

Troubleshooting already performed:

• Updated NVIDIA RTX A2000 driver to the latest available version.
• Installed the latest Intel Management Engine driver.
• Installed the latest Intel chipset drivers available from HP.
• Updated Windows completely.
• BIOS is already running version T50 01.06.12 (latest available on the HP support page).
• Attempted to update the BIOS again, but the update failed with an internal error because the same BIOS version was already installed.
• Checked BitLocker status before attempting the BIOS update.
• Ran:
- powercfg /a
- powercfg /requests
- powercfg /devicequery wake_armed
- powercfg /energy
• No process or device is preventing shutdown.
• The workstation is in its original factory hardware configuration.
• No hardware has been replaced or modified.
• Installed the latest available Intel Management Engine and chipset updates from the HP support website without any improvement.

Additional information:

The issue has been present for several months.

The workstation is completely stable during normal operation and under heavy workloads. The only problem affects the power-off and restart sequence when PCI Express Power Management is disabled.

Questions:

1. Is this a known BIOS or firmware issue affecting the HP Z2 G8?
2. Is PCI Express Power Management expected to be enabled by default on this platform?
3. Could this indicate a motherboard firmware issue or a PCIe power management compatibility issue with the NVIDIA RTX A2000?
4. Has anyone with an HP Z2 G8 experienced the same behavior?

Any suggestions from HP engineers or other HP Z2 G8 owners would be greatly appreciated.

Thank you.