ASUS ROG Z790 Hero PCIE x16(G5)_1 slot suddenly won't detect GPU

[JG2Springer]

Hey there,  My Z790 Hero suddenly wont detect my Asus RTX 4090. I has been working without issue for months. Full disclosure, the 4090 is in an EK Waterblock, and never had an issue. A few days ago I went to start up My Pimax Crystal software, and the screen went black and the computer froze. Upon rebooting, I got the notorious D6 error and the white VGA light. I cleaned the slot, as well as the GPU.. nothing... updated my Bios (twice just to be sure) igpu on  my 13900KS works fine.  Interesting thing is, I can put the GPU on the _2 slot, and it works (x8 though) . This is a custom water loop, that I have already torn down half a dozen times trying to figure out what the issue is.  Ram is Gskill 8200 DDR5 48gb single kit. I have tried removing and moving around the RAM as well as cleaning it and the slots. Still nothing. Uninstalled and reinstalled the Nvidia drivers while on the _2 slot.  Anyone got any suggestions? card, ram, motherboard have worked flawlessly for months.. all 3 M.2 slots used by Samsung 970 1TB nvme sticks.. never had any issues there either. and card was running on _1 slot at x16 speed before the crash. Power cable has been checked ( but the GPU works in the _2 slot, so...)  Any thoughts or suggestions?

[Jiaszzz_ROG]

Hello @JG2Springer 

Thank you for reaching out to us.
Based on the mentioned Q-code D6 and VGA Q-LED, it indicates an issue with the graphics card during the boot process.
Could you confirm if the graphics card is connected via an extension cable or adapter?
In addition to the Clear CMOS suggestion and verifying if the graphics card’s VBIOS is also updated to the latest version, given the multiple troubleshooting steps you have tried, please try cross-testing another graphics card in the problematic PCIEx16(G5)_1 slot.

Thank you

[JG2Springer]

Jiaszzz_ROG, 

Thank you for taking the time to respond. So I have tried 2 different extension cables both work with the 4090 in _2 slot. I have now tried two more power cables. Again, both work in _2 slot.  I brought home a 3090 from work and, just finished testing. With both extension cables and multiple PCIE power cables, the graphics cards work in _2 slot. No combination has allowed for any GPU to show up in bios in the _1 slot... I cleared the CMOS every time I made a change whether it be power cable, extension cable, slot, or GPU. There appears to be no life in +1 slot.  Not sure what to do next. Do I start tearing my sweet rig down?

[JG2Springer]

Jiaszzz_ROG, 

Thank you for taking the time to respond. So I have tried 2 different extension cables both work with the 4090 in _2 slot. I have now tried two more power cables. Again, both work in _2 slot.  I brought home a 3090 from work and, just finished testing. With both extension cables and multiple PCIE power cables, the graphics cards work in _2 slot. No combination has allowed for any GPU to show up in bios in the _1 slot... I cleared the CMOS every time I made a change whether it be power cable, extension cable, slot, or GPU. There appears to be no life in +1 slot.  Not sure what to do next. Do I start tearing my sweet rig down?

[JG2Springer]

SO.. went one step further as I have wanted the Hero BTF for some time now, I purchased a Z790 Hero BTF MB... set everything up, and same issue... sort of.. since there is no physical G5_2 slot... I was looking forward to see what happened... Plugged my GPU into the G1 slot, and some very interesting things happened.  In Bios..  G1 shows not device... and the M.2_1 slot shows @ 8x (there is no NVMe in the M.2_1 slot) and if I set the PCIE to x16 under advanced settings.. I can only see my display using igpu. If I set the PCIe to x8/x8 or PCIe with M2 ( says PCIe will run at 8x) I can get into windows.  Once in windows with my deticated GPU.. HWINFO64 shows the GP+U is connected to PCIe x16 G5_2 not G1

[Jiaszzz_ROG]

Hello @JG2Springer 

We apologize for the delayed response due to the recent local holiday.
Based on your previous experience with the ROG MAXIMUS Z790 HERO, you mentioned that test with two different extension cables to connect the GPU.
Could you confirm if the current issue you are describing also occurs when connecting the graphics card through extension cables?
We advise against connecting the GPU to any extension cables or adapters to avoid impacting the qualities or compatibility of the extension cable itself.
Please directly connect the GPU to the PCIEX16(G5)_1 slot, checking if the BIOS has been up-to-date, and checking the result again after clearing CMOS.

Additionally, since it is difficult to verify how third-party software captures and presents connection results or related data, if there are any discrepancies shown, we suggest cross-testing with different software to confirm the results.

Thank you.