Diagnose Wired LAN issues on the ASRock Z390 Phantom Gaming 4s/AC
Diagnose Wired LAN issues on the ASRock Z390 Phantom Gaming 4s/AC
Hey there! I’ve been dealing with this problem for about six weeks now. Here’s what I’ve got so far: My PC uses an ASRock Z390 Phantom Gaming 4S/AC motherboard with an Intel i5-8600K processor, 8GB RAM, and a Windows 10 system running RX 570. The main reason I opted for a brand new build was because the processor came free, and the only compatible board I could find was expensive.
The problem started with the onboard LAN port not working properly. It would randomly flash the orange and green indicator lights for about a second every few minutes. I tried several fixes—rebooting, disabling the built-in Intel Ethernet via BIOS, turning off the Wi-Fi, swapping cables—but nothing seemed to help.
I also checked the motherboard’s BIOS settings, but nothing changed. I even tried updating it, but the BIOS version was stuck at v1.00 and didn’t recognize the 4S/AC chip. When I searched for a driver update, I realized the board is labeled as Phantom, not ASRock Z390. It wasn’t listed on ASRock’s site either.
After some digging, I found the BIOS update through a Reddit thread and a website called Ibuypower. Still, the issue persisted. The network lights disappeared after a brief connection at 100MBPS, which made me think it might be related to the indicator lights.
I’m running out of ideas. My USB network adapter works fine, but the motherboard’s behavior is odd. I’m starting to wonder if there’s a simple fix I missed. Anyone else have faced this situation? I’m getting really frustrated.
It performs the green and yellow flash but has no internet connection.
The port's illumination will flash green and yellow briefly, but if it doesn't, the warning signs stay dark.
The LAN port is linked to a specific device or network. I've checked various cables and devices without success.
The lights may dim or fluctuate. The same connection functions with the USB lan adapter while connected to the switch, and I maintain a stable internet connection on my older PC.
Good news means almost everything else is eliminated except for a faulty onboard NIC. Unfortunately, it’s likely your device has a defective NIC. You may need a PCIe card to enable wired internet, though you should have gotten a good price on the board. If the unit is new or was previously sold as working, try returning it via RMA or ask for a partial refund from the seller.
USB lan port refers to an adapter that connects USB devices to Ethernet without a wired link. Check if the built-in network card appears in Device Manager under network adapters. Test a bootable USB with Ubuntu to see if it behaves similarly with both the internal and USB adapter.