Don't know if this has been resolved yet, but Asus Q-Code 40 means your PC has awoken from S4 sleep. What happens is in Windows 8/8.1 a feature called Fast Startup is on by default, it works by saving system info to a file upon shutdown so when you start your PC again, Windows uses that system info to resume your PC instead of restarting it. To disable this, right click your start menu and go to Power Options, then select Choose what the Power button does, then under Shutdown settings you can disable Fast Startup. Also, disable Fast Boot in your BIOS as well, it will be in the boot section. Answer from JayNew on forums.tomshardware.com
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Solvusoft
solvusoft.com › en › errors › device-manager-errors › microsoft-corporation › windows-operating-system › code-40
How To Fix Code 40 (Error 40)
November 30, 2025 - Typically, Code 40 errors are caused by a corrupt or missing 40-associated file, sometimes due to malware infection. Obtaining a new, uninfected copy of your Windows 10 file will usually resolve the problem.
Discussions

ROG Maximus X Hero Q-Code "40" Always Show at the ... - Republic of Gamers Forum - 766799
Hi ASUS ROG members, I bought an ROG Maximus X Hero motherboard and is curious about the Q-code shown at the motherboard 7-segment display. Each time I power up my PC, the Q-code shows "40". I restarted my PC and the Q-code shows "A0". Please advise : 1. What is Q-code "40". More on rog-forum.asus.com
🌐 rog-forum.asus.com
March 7, 2024
Motherboard error code 40, need help
🌐 r/pcmasterrace
2
1
May 3, 2020
Asus Q Code 40, no video out from GPU. 11 hours on this and I'm exhausted :(
I managed to grab a Maximus XII Hero on amazon warehouse for $160 Well, this is the first red flag. I'm going to guess the reason it was returned, and the reason it was sold for 1/3 retail pricing, is that it never worked in the first place. Also, Z490 requires a BIOS update to run 11th gen, which I'm guess is another issue that needs addressed first. More on reddit.com
🌐 r/buildapc
8
4
August 4, 2021
X570 Aorus master and Post Code 40
Do you have any kind of overclock applied? More on reddit.com
🌐 r/gigabyte
9
2
May 11, 2021
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PCPartPicker
pcpartpicker.com › forums › topic › 142061-asus-x99-a-q-code-40-sometimes
Asus X99-A Q-Code 40 sometimes - PCPartPicker
40 Q-Code: Pc was booted / boosted via a Windows controlled method (Usually from deep sleep, restart, Hibernation etc)
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Error Vault
errorvault.com › en › troubleshooting › device-manager-errors › microsoft › windows › error-40_code-40
How to fix Error 40 (Code 40) - Windows cannot access this hardware because its service key information in the registry is missing or recorded incorrectly.
Error name: Code 40 Error number: Error 40 Applies to: Windows 10, 8, 7, Vista, XP Description: Windows cannot access this hardware because its service key information in the registry is missing or recorded incorrectly.
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Asus
rog-forum.asus.com › t5 › z370-z390 › rog-maximus-x-hero-q-code-quot-40-quot-always-show-at-the-mobo-7 › td-p › 766799
ROG Maximus X Hero Q-Code "40" Always Show at the ... - Republic of Gamers Forum - 766799
March 7, 2024 - Windows 10 with fast boot enabled loads from "cache" on the disk making it faster. Qcode 40 is letting you know that the computer woke from hibernated state or what it thinks was hibernated.
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Error
error.info › windows › driver-40.html
Windows Error Code 40 Windows cannot access this hardware because its service key information in the ...
Windows cannot access this hardware because its service key information in the ... error message. In attempting to interface with the device you are trying to run, Windows ...
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ErrorTools
errortools.com › home › drivers › quick solution guide to error code 40
Quick Solution Guide to Error Code 40 - ErrorTools
March 25, 2022 - Error Code 40 – What is it? Error Code 40 is a device driver error that users encounter on any Windows 2000 and later operating systems. It occurs when the peripheral device that you connect to your PC cannot be accessed due to a change in the system registry. This is due to the presence
Find elsewhere
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Reddit
reddit.com › r/pcmasterrace › motherboard error code 40, need help
r/pcmasterrace on Reddit: Motherboard error code 40, need help
May 3, 2020 -

I just finished building my computer and occationally when I turn it on, the computer doesn't boot. The Error code on the board is code 40, and the CPU debug led it lights sometimes. I need to restart the pc 3-4 times and then the error goes away and the computer works normally.
My specs are:
Cpu: Ryzen 9 3900x
Mobo: Msi meg x570 ace
Ram : Corsair vengeance pro 2x16gb @ 2666MGz
Graphics: Geforce 2080 Super

I didn't make any changes in the bios and its runnin ght most up to date stable version.
Any one knows why this error could be occuring ? On install I made sure there was no pins damaged on the CPU

Thank you.

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Reddit
reddit.com › r/buildapc › asus q code 40, no video out from gpu. 11 hours on this and i'm exhausted :(
r/buildapc on Reddit: Asus Q Code 40, no video out from GPU. 11 hours on this and I'm exhausted :(
August 4, 2021 -

Hey! So this is probably my last case resort before I start tearing the system apart and completely rebuilding it with a new motherboard. I recently picked up the bestbuy ASUS 3080 pc and decided to transplant the components with existing components from a ryzen 5, 580x build of mine (ram and psu into a new case, cooler, and motherboard. I managed to grab a Maximus XII Hero on amazon warehouse for $160 so I centered the build around that and it came pretty much brand new.

Now to what's been making me feel so defeated: I spent about 11 hours disassembling both PCs and building two of them again. However when I tried booting up the PC that I was planning on using as my main driver, it boots and cycles to asus post code 40 (which has something to do with waking from crashing) however nothing appears on my monitor. I replaced the 3080 with a 3060ti that I planned to put in the other PC for my brother to test if it was a video card issue, however the same issue persisted. All fans spin, no weird noises, and there's just no visual.

Does anyone know what's up? In the worst case scenario my motherboard is DOA which would be tragic. However I'm hopeful that this just has something to do with a BIOS update incompatibility due to the lack of either 11th gen support on this z490 chipset (although from my research there shouldn't be) or something to do with the 3080/3060ti being PCIE 4.0 in a PCIE 3.0 slot? Does anyone have any ideas for things I can try out outside of just replacing the motherboard?

Things I plan to try:

  1. Removing ram sticks

  2. Updating bios(?) no idea how since I can't get into BIOS

  3. Trying the old RX580

  4. Last resort, replacing the motherboard (I don't have any more thermal paste or sticky washers from arctic, so I'll have to figure out how to get more.)

Thank you so much for taking the time to read this, I'm sad and angry at myself for not testing on the bench before putting everything together and honestly just want something to display so I can work.

PCPartPicker Part List

Type Item Price
CPU Intel Core i7-11700KF 3.6 GHz 8-Core Processor $529.99 @ Amazon
CPU Cooler ARCTIC Liquid Freezer II 360 A-RGB 48.8 CFM Liquid CPU Cooler Purchased For $140.00
Motherboard Asus ROG MAXIMUS XII HERO (WI-FI) ATX LGA1200 Motherboard Purchased For $160.00
Memory Crucial Ballistix Sport AT 32 GB (4 x 8 GB) DDR4-3200 CL16 Memory Purchased For $120.00
Storage Western Digital Blue SN550 500 GB M.2-2280 NVME Solid State Drive $59.99 @ Newegg
Storage Crucial MX500 1 TB M.2-2280 Solid State Drive $114.99 @ Adorama
Video Card Asus GeForce RTX 3080 10 GB TUF GAMING Video Card $900.00
Case be quiet! Pure Base 500DX ATX Mid Tower Case Purchased For $79.99
Power Supply Thermaltake Toughpower Grand RGB 750 W 80+ Gold Certified Fully Modular ATX Power Supply Purchased For $60.00
Prices include shipping, taxes, rebates, and discounts
Total $2164.96
Generated by PCPartPicker 2021-08-04 10:23 EDT-0400
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Linus Tech Tips
linustechtips.com › computer hardware › cpus, motherboards, and memory
I have an issue with Q-code 40 always display on mobo - CPUs, Motherboards, and Memory - Linus Tech Tips
November 14, 2017 - Hi, I just build a new rig few days ago. What im facing now is an issue that Q-code always showing 40 on my Asus Strix x399 E-Gaming motherboard. My last rig used to showed Q-code AO on the motherboard and i think that is normal but now im facing the Q-code 40 and sometimes Q-code AA. I do lot of...
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Reddit
reddit.com › r/gigabyte › x570 aorus master and post code 40
r/gigabyte on Reddit: X570 Aorus master and Post Code 40
May 11, 2021 -

Ok, so I'm having a bit of a problem here. Every other startup I get a bootup motherbrand logo on screen and then display just fades out. Post code shows 40 but nothing is happening.

Sometimes, If I wait long enough. 10 minutes give or take, the computer boots up properly during the long weird ass boot.

I did several clean install and it started happening even with a backup windows drive.

A lot of the errors I'm getting are

*Event log error event ID 6008

*Volmgr error Event ID 161

*Kernel Power Event ID 41

*Event log Error Event ID 1101

*Bug Check Error Event ID 1001

 -----here are my specs-----

*Gigabyte X570 Aorus Master rev 1.0

*Ryzen 9 5900x

*16GB 8x8 3600MHz CL15

*EVGA 3080 FTW3 Ultra

*Inland Performance Pro 1tb Gen4 (game drive)

*Inland Premium 1Tb Gen3 (OS drive)

*Corsair hx1000i Platinum

I've been going through for a while now and I honestly don't want to deal with Gigabytes horrid RMA.

Please help.

EDIT: Pictures of event ID EDIT 2: Videos Showcasing what happens

EDIT 3: Solved it. It was windows Fast startup. I had to disabled it in the "Change what the power buttons do".

Man this journey was so damn weird.

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Eight Forums
eightforums.com › windows 8 forums › general support
Mobo give startup code 40 when booting? | Windows 8 Help Forums
April 19, 2014 - If that code 40 is a BIOS error message, then I do not believe its a Windows issue. If the motherboard won't post the OS isn't loaded so its not a factor. Your overclock may have been stable but if you have overstressed your hardware it can become unstable. Back it off a bit and see if the ...
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Asus
rog-forum.asus.com › t5 › x99 › q-code-40-while-being-in-windows › td-p › 664995
Q-Code 40 while being in windows ? - Republic of Gamers Forum - 664995
March 6, 2024 - Fast boot is enabled in windows 10 by default. ... Hey, Thanks for the info. Yes it is "40" and fast boot is disabled and this q-code sometimes pops from a cold boot (no hibernation).
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Quora
quora.com › How-do-I-Fix-ASUS-Motherboard-Error-Code-40
How to Fix ASUS Motherboard Error Code 40 - Quora
Answer: The motherboard is the core factor that holds your computer’s components. So if the motherboard gets an error, everything falls apart. Asus error code 40 is a very common one. The error generally relates to the Asus motherboard issues which stop your device from functioning normally.
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H|ard|Forum
hardforum.com › [h]ard|ware › motherboards › intel mobos
Intermittent Asus Q-Codes 40 and 00 | [H]ard|Forum
May 8, 2016 - I see the BIOS splash screen and then the machine boots, but the screen is black or: no BIOS splash, and the monitor is flickering between really dark and mostly dark. A reboot always solves the problem. 2.) Machine boots and runs fine, but displays Q-Code 00 on the mobo: CPU not detected. I have ...
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Overclockers
overclockers.com › home › forums › hardware › motherboards › intel motherboards
Q-code 40 on Asus p8p67 Deluxe | Overclockers Forums
April 2, 2016 - That is where I would start... ... q-40 is memory related but also looks a lot like A0 which is HDD/SSD initialization . As for boot order the newer OS like windows boot manager as boot device.
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Linus Tech Tips
linustechtips.com › the workbench › troubleshooting
Asus X99 Deluxe 2 Q-Code 40 - Troubleshooting - Linus Tech Tips
July 28, 2016 - The new motherboard with installed windows 10 os can't install wifi driver · derekchan · 5 hours ago Posted in Troubleshooting · 4 · Why can certain LLM models trigger coil whine on the GPU and some cannot? Seamus X · 7 hours ago Posted in Troubleshooting ·